There are list-makers and there are calendar-followers. Either way, one eventually has to look ahead the next eight to dozen hours and figure out where the day is taking you, and what you plan to make of it, and accomplish during it. I've found that visualizing the day as a circle, resembling an analog clock, is helpful in ways that a straight top-to-bottom list doesn't quite manage.
Step 1: Recognize the Discontents of the List
The straight list can be a thankless task master. The list can grow, and there is something Hydra-like about a completed task: strike one task, and two other tasks rise in its place. One simple hack to the list approach is to add approximate amounts of time to each task — to get your priorities straight, and to help you realize just how much is ahead of you. But that math (2 hours here, half an hour there, all tolled) doesn't quite connect, at least for me, with the day the way the circle calendar does.
Step 2: Start With a Circle
Instead of a straight list, try using the circle to help you visualize the day. Even if you haven't looked at a "traditional" two-handed clock in a decade, the circle has benefits that a digital-readout clock does not. The symmetrical alignment of 6AM and 6PM — or whenever it is that you wake and, a dozen or so hours later, begin to phase out of work mode — is more immediately apparent when laid out as a circle.
Step 3: Lay Out the Day
Somewhere someone reading this may think, "Oh, cool, I'll print out a bunch of circles." I'd suggest not doing so. There's a benefit in drawing the circle by hand as part of the process, dropping in the four compass-point hours of 6, 9, 12, and 3. If you treat the circle as a pre-set container, then you'll just start dropping projects in. Starting by drawing the circle itself reinforces the inherent constraints of a given day.
Step 4: Pace and Optimize
Only once the 4 compass points and additional 8 hour markings are set in place should you start assigning tasks to particular time slots. Be sure to leave room for breaks and meals. Try to alternate short and long periods of exertion. And when there is travel to be dealt with — a bus ride, for example — consider adding something that can be handled at the same time, like document consumption or simple email chores.