1) Write everything you want to do in a numbered list. Just write anything, it's better to have too much than too little.

2) Label each with a letter, using the following legend: A- This will have a majorly positive or negative effect on my life depending on whether or not it is done. B- This will have a majorly positive effect on my life if done. C- This prevents something bad. D- This will fail to have a major effect on my life no matter what.

3) Now your goal is to limit all these tasks to 30. Eliminate the least important task (a D) and repeat. When you finish with the Ds, move to Cs. Hopefully you will not have to eliminate As or Bs. 

4) Choose your 3 priority tasks for the day. 

5) Write all 30 tasks on one side of a paper.

6) Cross off tasks as you finish them. Label the other side of the paper, "Capture", list ideas you have. 

7) Use the back side of the paper in place of 1. Repeat steps 3-6 daily. If having trouble with 3, repeat 2.

Change systems as little as possible.

If you want to write more than 30 tasks on a list, you are either not finishing enough tasks, or committing to too much. Both answers are equally valid. Choose which one suits you.

The priority tasks are the first tasks to complete in a day, not the only tasks to complete.

After the priority tasks, complete the most urgent tasks first and less urgent ones later.

Daily habits are urgent.

It's a good idea to have a separate space for project plans. Don't get carried away though.
Make sure to actually add project tasks to list.
A "Back-Burner" list might work, but only if it's regularly tended to and never exceeds 30 ideas. I personally have never done this, too much work, and too much chance for stagnation. This may work for some particularly busy individuals though.