If you have access to a computer and a smart phone, I would sign up for a gmail address (you don't actually have to use it) and start using google calendar. That's what I did in June when I got my first smart phone, and it has been great. I got an app called Calengoo, because it was highly rated and because it works with google calendar.
Now, wherever I am, I can check Calengoo on my phone, or Google Calendar on a computer, and can see everything I need to do. On Google Calendar, I can color code things (the colors don't work on Calengoo, but maybe I just haven't figured that part out). Red is for me, blue for one kid, yellow for the other, etc.
Also, on both I can use the tasks feature, which is great. I have a list called "shopping" and I put things I need to buy on that (I do errands every Saturday morning). I have one list called "to do", and another one called "house" (things that need to be done around the house. I will probably keep adding lists. You could have task lists like school stuff, work, rental properties, etc.
There is another app called Evernote (that you can use online and on a smart phone) that is great for note-taking. I use that for other lists and notes I want to take on things for work, etc. You organize your lists in notebooks by topic. It can do lots of stuff I haven't tried yet; people rave about how great Evernote is.
Last suggestion is keep a file for every day of the month. If I'm going to need something on the 11th, it goes in the 11 file, and there it is, the day I need it. You could check out Getting Things Done (a great book about organization) to learn more about that.