Bec,
To answer the question you posted in my gym log....
Well I started out with 1, 3 and 5 pound weights. After a time you just feel it is time to go to a higher weight. You try it, and if it works you keep going with it. It just takes time.
I've also found that I can do much higher weights with on the lower body workouts than on the upper. For side raises, It's all I can do to finish a set with 3 pounds.
Do I understand correctly that you have a personal trainer? How often do you see him/her. Is it worth the time and expense? I'm pretty curious...I'm doing everything on my own from pictures in books and websites, and guessing by how I feel during an exercise. Having access to a PT would be a big bonus.
BTW, Nat shared these links with me early into my BFL program. They give a variety of exercises, and show videos on how to do them:
http://www.exrx.net/Lists/Directory.html Lots of things to explore. If you click on muscle directory it will list muscles, then give exercises for them.
http://www.2-fit.com/video/index.html More videos arranged by muscle groups
How's your workout routine going?