Get a book called Natural Fertility by Francesca Naish. It's good, comprehensive stuff. She also talks about lunar cycles which can make a difference for some people.
I think taking a class would be very useful.
Personally, I find CM is the best indicator of O time, but of course this is different for everyone. If yours is cooperative (lol!) you'll find that it gets creamier closer to O time, then becomes like the consistency of egg white at O - hence the term EWCM.
If you like, go to the Fertility Friend website (like Kitten suggested) - they have charting tutorials as well. They give you 1 month free to try it out then I think it is relatively inexpensive to use. (Though I just made up my own charts based on one that came with my basal thermometer when I bought it. I just made the chart on the puter and added the bits I liked.)
Good luck!

ETA: I would suggest using alternative contraception all the time for the first few cycles. Just til you get the hang of it and so that you're more relaxed! (Also, you'll no doubt need the practice using the diaphragm at first too, LOL!)