the serratus will work while doing the following: bench press, dips, pull over, dumbell flies(a bit), flies a bit, push ups using the push ups grips. but it also seems that having a wide and big latissimus dorsi muscle helps to make the serratus visible. if you want to target the serratus specifically here is what you need to do (besides having big lats):
when you bench as you raise the bar try to raise the bar more by pushing your shoulders forward, you can do that also with dumbell presses, you can even press without bending your elbow just pushing with your shoulders up and down (sort of like shrugs but front/back rather than up/down), dips will also do the job, inclined dumbell press, and pull overs. i have another exercise on the chin up bar but hard to explain i will give it a try:
hang down on the pull up bar and try to lift your body up keeping your arms sort of straight (swinging a bit helps) and try to lift up like you are doing a pull over movement your aim is to try to make your arms horizontal your shoulders must be pushed forward as you push up. your legs straight pointing down your body will not be vertical as you push up it will tilt a bit. anyways this is not a very important exercise.
