I started doing a combination "spin & sculpt" class that's 40 mins on the bike and 20 mins of weight training. They also have various classes that do weight training. I personally prefer the classes since they're more structured. But if I just do a spin class, I try to put in some arm work on the weight machines. I can't really say I'm an expert there, I just do them at the weight I can handle and for 3 sets of 10 reps each.