Push ups are great, overhead presses, tricep dips, lateral raises... All kinds of exercises. Go to sparkpeople.com. It's a free social network site with lots of exercise demos you can look up (including videos). Cardio is important (and a healthy diet), because you can build up all the muscle you want, but if there's fat covering it up, no one will ever know. =)
The best thing if you're slimmed down would be push ups. They work everything. Swimming is also great for the arms. I had wonderful triceps when I swam a couple of days a week.
at 4:11 AM on Nov. 2, 2010