When you are doing biceps exercises, do you get a deep lactic acid burn in the belly of your biceps? Or do you feel like you didn't get much in them but for some reason your shoulders are tired or sore after your workout? The exercises that have been mentioned are awesome, but if your form sucks, you don't straighten your arms all the way, and your shoulders are rotating to get the weight up, then you still won't get the most benefit. If so, just lower the weight a bit and do some sets where of 12-15, with strict form. Don't sling the weight, lean back, move your shoulders, just move your arms from the elbows down. Elbows should stay down if doing standing or seated curls. If doing preachers, you shouldn't have to pull back with your whold body to get the last reps in. Focus and do enough reps that when you feel that burn start, prob around rep 7-9 or so, do 5-10 more. those extras are the key to make sure you are hitting your target muscle. Pick 2 exercises, and do 3-4 sets of 10-15, controlled reps where at least the last 5-6 burn like hell. If you have to lower the weight to get the last set, fine. Don't do anything else for them and let us know how they feel the next day. As you learn the form for the exercises and feel the burn, you can start to go up in weights. But you should be able to feel that burn even when doing heavy weight and lower reps.
Don't worry about having to lift lighter. I'm definitely not the strongest guy in the gym, nor do I want to be. But I had to take the time to learn how to blast the targeted muscle and get the most results with lower weights. You become more efficient and it helps reduce chances of injuries down the road. You should also apply this principle to all your lifting if you goal is to devlop your physique as opposed to just be a poerlifter. Powerlifting is a complete different ball game that plenty of others can help with that. Learn how to hit your muscles correctly, then as strength develops, you can do low reps, heavy weights, and know how to apply the stress to the right areas.
Let us know what kind of routine you are currently doing, exercises, sets, reps if you have any other questions, we can help.