I recommend David Allen's Getting Things Done (GTD) methodology. I use it with OmniFocus, but there are a number of other tools available.
The process is straightforward (collect, process, organize, do, and review) but what I found most helpful was getting everything out of my head so I could stop worrying about forgetting anything.
The process is straightforward (collect, process, organize, do, and review) but what I found most helpful was getting everything out of my head so I could stop worrying about forgetting anything.