Both supersets and dropsets are very effective. It is good to superset opposing muscle groups such as bi's and tri's. I usually superset my arm exersizes, and find that I actually have more strength if I do than if I don't. A superset for shoulders could look like,
Military Press (8-15 reps)
DB Shoulder Press (8-15 reps)
Trust me, your shoulders will be throbbing after doing a few supersets of this sort! Supersets also shave a lot of time off your workouts. I usually superset shoulders and back, bi's and tri's, and leave my chest by itself.
A dropset is where you do a light weight/high rep set after doing heavy sets of an exersize. The dropset is performed directly after the last heavy set with no rest in between. An example would look like,
Incline Pressx3 (4-6 reps) ,after last set 1x10-20 reps
You will probably have to do a very light weight on the dropset because you have used up a lot of your strength on the heavy sets.
scott