I keep a pretty extensive todo list. I don't really know if it helps me do more things or be more reliable, but it certainly comforts me.
But how do I actually pick items off it? How do I actually decide what to do? Here are a few of the strategies that I use, for better or worse.
I apply these strategies only after filtering out items that I simply cannot do because of my current circumstances. e.g. I can't make phone calls from the tube.
**Meet the deadline**
Something needs to be done today, so I'll do that. The beauty is its simplicity.
**Do something fun**
I'll look at my todo list and after careful and thoughtful consideration of priorities, time frames, personal responsibilities and life goals, will do whatever I wanted to do in the first place. 
**Shorten the list as much as possible**
When I go through the list trying to get rid of as many items as possible, aiming for the shorter and easier ones. Generally happens in a mad panic on a Friday afternoon. The biggest danger is that I make a mistake in guessing how long something will take and end up stuck on one task forever.
**Kill the oldest item**
This thing has been on my plate *forever.* If I do it now, I'll feel like a Much Better Person. 
**Finish off one project**
Because it's cool to reach an actual outcome, rather than eternally making progress. This is almost always impossible to do.
**Now or never**
If I don't do this particular todo right now, I know I'm never going to come back to it.
**While I'm doing this I might as well...**
Not so much consulting my todo list as letting my mind's vagueness and the distractions surrounding one task lead me into another. Often ends up as productive and valuable time spent. I guess I irrationally believe that conscious choices are better, somehow.
**Tackle the most daunting task first**
Often the oldest item is the most daunting, but that's not always the case. I guess I could expand "most daunting task" to mean "the task I find myself thinking about the most". Thinking how one should really do a thing after one has already decided to do a thing is a waste of valuable energy, so sometimes it's better to just do it.
**What will I not naturally do?**
A lot of the things on my todo list are things that I'll get around to in due course anyway. Part of the power-up that a todo list grants is the ability to choose to do things you wouldn't otherwise do. These don't have to be daunting things, they can be fun, or exploratory, or mundane. Something like writing a small program in an interesting new programming language, or finally getting to grips with what a financial derivative really is. These things often fall into the "important but not urgent" category.
**Personal utility**
What thing can I do that will improve my life the most? I use this one the least, although arguably it is the most rational.
There's some overlap between these categories, but I think they are different enough to be useful to me in improving my self-awareness, and perhaps even in making better decisions about how to use the time God has given me.