I had a few troubles with the guy who does my gym program, too. He stuffed me around a little (left the program at home 2 days in a row etc). Then turned out that he didn't even consult my previous program when he designed the new one and so my new one wasn't a progression at all. I'm going to give him one more chance...

I don't know that anybody can tell you how much weight to use. It is a matter of trial and error. Basically... See how many repetitions and how many sets you want to do in your program (8-10 reps for 3 sets is pretty typical) and then... Try it with a weight. You want to be really struggling to do those last two or three repetitions in a set. If you can do them then put the weight up. If you can't do more than a couple repetitions then the weight is too heavy so you want to put it down. It can help to write down how many repetitions of each set you complete (and the weight you used) so you remember what weight to start with next time. Then you also have a record of the progress you have made.