Free weights are key.
The down motion will build bigger muscles than the up motion. Release slowly and count 3-4 seconds till extension. Make sure you're doing the full range of motion or you're robbing yourself of gains.
Dumbbells, 1 arm at a time, bicep curls off your knee. 12 reps each set, 4 sets. Should struggle on the last 2 reps of 1st set. Do rows for triceps. Several different excercises for each is key. Don't forget Deltoids as those make the arm look bigger.
http://www.bodybuilding.com/exercises/ for range of excercises