But, so far, my system consists of three different todo lists:

• Daily+weekly todo lists — the larger important things I need to be sure to get done, either today, or at a specific deadline in the future (eg. the stuff you'd put on Google Calendar, for instance)
• Today's minutiae — smaller tasks that are to trivial to plan ahead or analyze afterwards... but are perhaps the larger tasks broken down into smaller steps, so it's clearer what the immediate prerequisites are, to give a better idea of how to plan today's time (eg. to make sure that, when I need to wait on someone else for something, that I let them know ASAP that I need it done, instead of waiting until the end of the day) (eg. the smaller stuff that you'd put in Notepad just so you remember to get back to someone who called you, for instance)
• Behavioral changes — changes I'd like to make to my daily or weekly routine, that should eventually become habitual, but in the short term I need to conciously try to remember and make sure I'm doing the desired task on a regular basis whenever appropriate. Note that I shouldn't put too many things on the list at once... perhaps 5 things at most. If this can be an effective system for learning new habits, then I can always delay a new-todo until later, once items on the current list have become habitual.