I like the way missjane posts her logs. That way, if you have 3 sets of 15 reps but you use different weights on your sets, it's easy to see.
Alternately, if you do 3 sets of 15 reps and lift 50 pounds for every rep of every set, you can say 3x15x50.
And if you do an exercise with 20-pound dumbbells in each hand, you can post your exercise as, say, 3x15x20e.
Also remember that if you're using one of the big barbells (the olympic ones), they weigh 45 pounds - don't forget to include that in your weight.

So if you put a 10-pound plate on each end of the barbell, that'd be recorded as 65 pounds, or 3x15x65 (if you did 3 sets of 15 reps). Some of the bars are smaller, though, so it's good to know which one you're using.
Does that help?