As Gruber said in his answer, Agile methodologies will suit you well. If you decide to adopt Scrum for yourself, the key thing to remember is that no planning should be done during an iteration. This means that at the beginning of an iteration you'll plan what you'll be doing for the next 2 or 3 weeks (the iteration length can be adjusted to your needs, but usually 2-3 weeks works best), and then you shouldn't change any of your tasks, which includes not implementing anything new that wasn't planned beforehand.

Once an idea comes to you, write it down somewhere and try to forget about it. The idea might seem brilliant at the moment (or at least better than your current task), but it might not seem so good some time later. Give your ideas time to settle, then come back to them and try to assess them again with a fresh look (probably at the beginning of an iteration when you need to plan the next few weeks).

From my own experience, I worked in a small software company which suffered a lot because of such idea overflow. We had new tasks before we had completed the previous ones, so eventually nothing was getting done. We had a bunch of incomplete stuff that wasn't working properly. But after we adopted Scrum and followed the key rule (which in our case was the same as I recommend to you: don't change the plans during an iteration), the situation improved significantly and we were surprised at how much we managed to accomplish.

And one more thing that I think could be helpful. Always assume that your new idea is a bad one. Don't rush to implement it, take your time. This combined with Scrum could really work for you.

Update: From your edit I think it's fair to assume that your focus is more toward making new ideas rather than working on a current one. If that is so, the real problem is to stay focused on the current task. I suggest you break your working hours into two parts: when you actually work on your current task and when you think of new ideas. You could try to see what sequence of the two works best for you (for example, work on a task for 6 hours and then spend 2 hours on the ideas, or have 2 hours for ideas in the middle of the day).

I too generate a ton of ideas- most bad. I wake up in the middle of the night with random ideas. I always write them down but for me it doesn't matter where. Just putting them somewhere gets them out of my head. If I don't write them down then they are always distractingly dancing around the back of my head chanting, "don't forget me!" So I have ideas in old emails, notebooks by my bed, Evernote and most often in a private blog.

To keep myself from chasing new ideas I just ask myself, "would I pay somebody else to do this?" If you would pay somebody else to do it, great, pursue it. Still have too more ideas worth pursuing than time to pursue them- then starting paying somebody to do it. As long as you were honest in your assessment of value it will be money well spent and will offer a return. Methodologies and systems are great but I find my own checkbook to be the greatest (and most honest) filter for idea value.

You could also give your ideas away. Some people are great with ideas, some horrible. Often the people who aren't creative or outside-the-box thinkers are excellent drones (not meant in a bad way). Give them the idea and let them work on it. Heck, even let them have all credit for it. If they can get it done and it adds to the sum of the project you are working on it will still benefit you. Best to see the idea come to fruition regardless of the person getting credit for it.

And don't forget about personal time value. If you are spending time on a project you would not pay somebody else to do, you are valuing their time more than your own. Is some minor (but stubborn) tweak to an auxiliary feature really worth a week of your life? All of our life clocks keep ticking down- don't waste your time.

One of the things that you should keep in mind that ideas, when they come, are the highest level and as a result they sound extremely attractive. It's when you start digging deep into the idea with market research, competitive analysis, implementation challenges, time and resources, etc. you'd come to a conclusion more often than not, that it's not that great or original idea after all. Remember - Devil's in the detail.

My version of "idea discipline" involves: 1) limiting the number of active projects; 2) rewarding the completion of projects with new ideas; and 3) avoiding stagnation with regular triage.

The problem is that coming up with new ideas is way more fun than seeing the old ones through. To deal with this I have four folders on my drive: Defunct, Ideas, Workbench, and Complete.

New ideas go to the Idea pile (I use plain text files for this). Workbench has the projects I am working on now, and should not contain more than three projects (your bandwidth may vary). Moving stuff from Ideas to Workbench is a pleasure and a privilege, but it requires I clear space on the workbench (by actually finishing things or by killing off stagnated projects).

I evaluate the Workbench projects daily. Completed projects go to Complete. A lack of progress on a project for some months puts it danger of being moved back to Ideas or to Defunct. About once a month I "cull" the Ideas folder to deprecate second-rate ideas to Defunct as well.

Here is another suggestion - first, as others have said, write down the ideas as they come, to offload them from your brain. A tool like Evernote also enables tagging of the ideas for easy retrieval later.

If a particular idea re-emerges at another time and/or in another context, then perhaps there is something to the idea that should be looked into, as it might reflect a genuine opportunity/need-gap. It is my experience that truly good ideas tend to be "sticky"...they emerge again.

As a backup, as others have mentioned, in case particular ideas don't re-emerge for whatever reason, scan the list of ideas from time to time to see which ones might still be appealing. It is not unusual for most ideas that appear good initially, to have blocking issues, typically execution/resource/fit/strategy related, when looked into more deeply.

So I would continue to work on the project as planned, write down the ideas as they come, and if an idea re-emerges during the project, investigate it and implement it if it looks promising. Otherwise, look for ideas in the list when you have time to implement something new, and see which ideas may be worth spending effort on. This way ideas will not be a distraction, but a means of systematic improvement.

I like to keep things simple. The best method Ive found for starting (and finishing) projects is to use a combination of deferment and planning.

Like you, I also suffer from idea overload. The thing is, over time I've realized that most ideas seem exciting in the present, but loose interest over time.

To combat this phenomenon, I always write down my ideas, but I never immediately act on a new idea. I let it sit for a long time.

Every month I'll go through my list and weed out old ideas that now seem uninteresting to me.

The second part of my system is planning. I only allow myself to work on a small number of projects per year and I always plan them in advance.

I like to work in three month cycles, so four times per year I'll go through my list and pick out the most promising ideas. Like I said earlier, these are never new ideas—they're always ideas I've kept around because I still find them promising. Those ideas will make up my project schedule for that cycle.

It does take some discipline to stick to the plan, but I always keep in mind that a good idea will stick around and I can always work on it the next cycle.

Hmm. Psychoanalytics? Are those never ending ideas just a way to avoid something else? Or escape something? Why? Or, why do you want to stop generating ideas? Do they bother you? Why?

You can go on.. and on.

"Why" is a good tool, though somewhat dangerous. You may find what you didn't want to find.. and why you didn't want it.

IMO.. ideas are a good thing. They prove you're alive.

The rest is about taking them (or yourself) seriously or not that much, and try alternatives.

I face similar and have gained benefit from the perspectives of two people specifically: James Altucher and Chase Jarvis.

James Altucher believes that idea formation is a process that we need to acknowledge and even goes so far to say that it is a good thing: we need to become an idea machine. He recommends forcing yourself to write down ideas every day. Keep a record of them and you won't lose them. But also by forcing yourself to have this routine, you use up a lot of that idea energy and it stops getting in the way of doing things.

Chase Jarvis also has an interesting viewpoint. He did an interview recently with Ramit Sethi, where he said basically the ideas come all day during the heat of battle. You can't stop them. But synthesis happens during the quiet times. So he "bookends" his day for quiet time. In the morning, he refuses to read email because that is "other people's shit". So he focuses on his own work and ideas and family in the morning. He also focuses on family and his own projects in the evening. In this way, he structures his day to avoid the constant barrage of wants and needs from people other than his family and his own projects.

Give these ideas a try, and see if you gain some control over the "idea machine".

Thanks for sharing your experience, and good luck!

Whenever something irrelevant to what I am doing pops in my head. I usually write it down in my journal. I usually would read through my journal once a day. Ideas, thoughts, feelings, anything. That's what a journal is for. It's where you can offload everything. It's also useful for remembering too, keeping track of events or a brief overview of the meeting with Co workers. I would recommend trying that.

I use tools like mind mapping and Evernote to capture all the ideas so I can get out of my head.

But when it comes down to what to work on, I have a clear vision and establish the priorities each week. I don't drop the project that I am working on to chase new ones because the project I am nearly finished will earn me money sooner than any new one.

Since the idea is now out of my head and in a mind map or Evernote, I can focus.

When I complete a project, then I can review my notes and decide which one to work on next.

If you truly can't focus because of all of the ideas, you likely need to work with a coach on a weekly basis.

"Captain Time" Garland Coulson