1. Try to get into the GTD habit, perhaps try out NirvanaHQ. Read 43F - Getting started with GTD...

   This allows you to free your mind by placing all those ideas in an Inbox and forgetting about them, as they are stored in that Inbox and they won't go anywhere. Don't trust online websites? Try to get a GTD workflow in OneNote, Evernote or more specific GTD software tools...

   The next step is processing these tasks into do-able actions, which you will plan for today, later and someday. Read this question I've asked about emptying the Inbox if you have troubles doing so...

   And the next step is to go through what you have to do and iterate and refactor above merciless.

2. Try to use time management, perhaps try out The Pomodoro Technique with Focus Booster...

   By planning to be working for the next ~25 minutes and getting rewarded a pause of ~5 minutes afterwards you will more easily start with work and manage your time better than just doing no work for the next ~30 of even ~60 minutes. You will get your work done and know that after a few iterations of ~25 minutes work with ~5 minutes pause there will be a bigger pause you scheduled. In those short & long pauses you can plan out all those distractions and longer non-productive activities.

   Other than that, it accompanies your GTD system in being able to decide what you will be able to do in a day. Just like the GTD system it allows you to review your time as well as tasks and refactor it so that the GTD & Time System works better for you...

Before I go do all the stuff that is listed at How do I deal with distractions when working on a computer? I take a moment to relax by doing something completely unrelated to the computer. I usually go get a haircut, have a head massage, clean up my room, cook a meal etc.; anything which you can find relaxing and that clears up your mind. The important bit though is not turn this into procrastination and once you are done, jump back right to your most important task and complete it to success.

Writing should work, but you need a little discipline around it. For me:

Making sure all your medium to high urgency items are written on one page really helps when prioritising them, and you need to set strict rules around prioritising, eg things to do in next hour, half day, day, week etc - and the way priority may increase as they get closer to deadlines. Once the rules are set, it is very easy to do this with all new tasks.

Once you have this list, a good thing to do each day is to deliberately choose a "quick win" task to get you motivated before tackling the highest priority task.

Don't do anything else until either it is finished, or you hit 90 minutes. At 90 minutes take a small break and a quick walk around to get the metabolism up a bit. Quickly check the priorities on your list to see whether anything else should be looked at. If not, continue on with the same task.

Only check for new emails or other distractions at the end of your second 90 minutes. This helps avoid getting sucked into non priority issues, and to be honest, for most purposes, responding a couple of hours late to an email is not a big problem.

Try to set up a timer. Start with small amounts of time. For example - 15 minutes. During this time you can't start any entertainment. Create account at your computer with no rights to visit some sites and start some programs. After this period of time do anything you want to do for the equal amount of time.

After 2-3 days add 5 minutes to the work period, and remove 1 minute from entertainment period. Your goal is 60 minutes of work and 6 minutes for the entertainments. This point is critical, and after this you should just get used to do things this way.

Good luck with that.