I use to-do lists, but you have to be careful--they can become a trap. It's so inherently satisfying to check stuff off and, each time you do, you feel you've really accomplished something. But let's face it--anything that can be reduced to a "task" on a list may not be where you should be putting much of your time. I've had "tasks" on to-do lists that shouldn't be there because they require long-term effort. It is all to easy to ignore them for that reason, but the problem is, they are the more important things to do and they tend to keep getting pushed off the table (I like the "for research" list idea, but worry that I, anyway, would tend to avoid looking at it).
On the other hand, to-do lists can be wonderfully helpful in the sense that, if you try to remember to do things (e.g., call a colleague, send a report, or whatever), your mind ends up juggling too many things and starts sending you these sudden, intrusive reminders (I get a kick of adrenaline when that happens). I found that, if I write those things down, my mind shuts up.
The old idea of the quadrant of activities (things that are both urgent and important, things that are urgent but not important, things that are important but not urgent, and things that are neither) has been, to my mind, very helpful. The ones that are neither can be, basically, tossed in the trash; I don't think anyone has problems with those, nor with the important but urgent. It's the important but not urgent things that get overlooked, and all too much effort is spent on things that are urgent but not important, and those are the things that tend to occupy to-do lists.
My strategy has been to either turn off the phone (if I can, or discipline myself to let the phone go over to voicemail), close email, and close the door. You also need to train yourself to focus. That was hard for me even though I have near-Asperger's ability to concentrate once I get going. It's the getting-going part that was hard. You just have to learn to shut out all the other things. I think it's helpful to set time aside to think about this mindfully (that's where the quadrants come in), and set a strategy that will work for you.
I know this all sounds kind of touchy feely, but this is an area where I think people differ vastly. What works for me might not work for others. I can't imagine being the sort of person who can be interrupted once I get going. Once I get going on something that requires a lot of concentration, the rest of the world disappears (I think the house could burn down around me and I wouldn't know it). So getting started is my "only" problem. I wouldn't have a clue how to advise someone who has trouble maintaining focus once they've captured it.