Mine start out a little high (1st day or 2) then they usually level out for the first half of the cycle, and then right before ovulation, I usually get a big dip and then after ovulation they go up.
fertilityfriend.com is a good site for charting your bbt. It also gives some pretty good info.
Those are good pre-o temps. Not all women, but a good handfull get a temp drop just b4 o. I am one of them thank goodness. It's a nice head's up to let you know o is very close. A surge in estrogen just b4 o causes the drop. Usually when you see the drop a pos opk is real close and o very soon. Not all drops are due to this though and until you get a good feel for charting, you don't want to rely on it. It may not show on every chart either. Once you o, you should see a climb in temps by .20 to .50 and it should remain higher than the temps you have now. If you don't miss a day for the next few days you should be able to see o pretty clear on chart. Nothing sucks worse than missing a temp and having them up the next time you temp, then wondering which day it rose.