Try to look at existing time management systems rather than starting from scratch and trying to reinvent the wheel. There isn't a number one tip for learning about your time management system to improve it, as it simply comes down to an effective study of how an improvement or a difference in your time system would improve how the time management system improves your time usage.
For example, (subjectively) the best time management system I've heard of is The Pomodoro Technique. There are a lot of people practicing this technique on a daily basis and have worked this out into large detail. Which means that there are numerous of discussion, reviews, tips and similar resources available. It's much easier to extend on an existing time management system and forming it your way, instead of taking the wrong tips as an advice and becoming less efficient than you could be...
For example, it's better to "look at where your time went" as this can tell you useful things than it is to "see what projects I spent the least time on" because some projects simply don't need a lot of time. Unless you were referring to equal-sized projects or tasks, but that's most likely not to be true. As for projects, it would be better to look at how much you progressed in the project relative to it's deadline. As that would give a goal-based look instead of a time-based, if you're not on schedule you could then just assign more time...
To reflect on the new title, it all comes down to comparing time management systems and see which one helps you get more things done as well as other personal constraints on time spent on certain contexts. :)