one of the most important tips you will ever learn, when it comes to exercise, is quality over quantity. i can't tell you the number of times i've stood in my gym with some of my fitness expert friends and looked in massive confusion as we try to figure out what a particular individual is trying to accomplish and what muscle group they think they're working. it's baffling. and funny, at times. in all seriousness though, you should always exercise proper form when training to maximize your results and to avoid injury.
hopefully your gym has trainers that you can ask questions of, so take advantage and ask one of them to spare 2 or 3 minutes to show you the proper form for your favorite exercises. if you want to get really in depth and access a ton of information, pictures, tips, videos, and articles about injury free training and proper technique, try my tried and true resource bodybuilding.com. The awesome staff at bodybuilding.com not only supply everyone with great products, supplements, clothing, and fitness gear, but they've gone so far as to document workouts by muscle groups with the accompanied description, photos, and/or video on how to properly and safely perform it.
go check them out to make sure you're training properly and injury free, but use this little cheat sheet, too!