I have wanted to write about deltoid workouts for a while now but never quite get to it. Out of all of your muscles your deltoids may be the most obvious to work in your workout. The muscles are very easy to isolate. To work your shoulders you have to remember that your deltoids have three heads, one in the front or lateral deltoid, one on the side, medial deltoid and one in the back posterior deltoid.
Any exercise where you are lifting in front of you works your front deltoid. This includes front raises, pullups and to some degree bench press. To work the side deltoid you can do side raises and there do actually isolate your side of your shoulder really well and make your shoulders pop out, widening your shoulders better than anything else. To work the rear deltoid I have always found that the best exercise is to lean forward and do a flye like exercise where you swing your arms out from underneath to a position right lateral with your upper body, try it out you will really feel this exercise a lot.
One mistake that many people make when working shoulders is using too much and doing to few reps. Try doing three sets of each of three exercises (one for each part of the deltoid) and do 10-12 reps for each exercise.
Take care of your form as well. I also find that most people want to really work their shoulders and will use bad form and swing that more than they should. Do not worry about the amount of that you are lifting instead try to concentrate on keeping the reps very controlled and a little slower than the time that it takes for reps of other muscle groups.
Deltoid workouts can be tough and hurt a lot the next day but in the end your deltoid muscles will make your upper body look a lot bigger so it is worth the effort.