1) fast reaction to the start buzzer (previous post)
2) strong push off the block (previous post)
3) clean entry into the water
4) efficient and fast underwater kick in streamline
5) powerful and smooth breakout
3) Clean entry into the water - To continue the start lesson, we must examine the way your body enters or should enter the water after you have successfully pushed off with a fast reaction time. The best way to describe this is by an analogy. If you ever watch track and field (athletics) competitions, you have probably seen the javelin throwers. A good javelin throw is not too high and not too flat, the arc of it is just right. In comparison to the swimming start, we are only focusing our attention to the second part of the arc when the javelin is travelling, with the help of gravity, back to the green grass stadium flooring. In order for the javelin to stick, it has to have the right angle, same as in order for a swimmer to enter with the least amount of splash the angle has to be just right. Think of it in terms of your fingers creating a hole in the water and your entire
4) Efficient and fast underwater kick in streamline - Sticking with the javelin analogy. High javelin arc will cause the javelin to travel very high up and then stick itself in almost vertical position, same in the start, if you jump too high up, you will enter the water and go very deep which will cause you to struggle to come back up, thus loosing the speed you generate off the start. In the same manner, low dive/low javelin throw, will cause you to enter too shallow, getting too much wave drag from the top of the water and surface prematurely. Each person has an ideal depth at which they produce the least amount of drag and it is at this depth you need to stay as long as you can keep the speed off the starting block going strong (~2-3feet/60-90cm). To help you with that, you have the underwater dolphin or breaststroke kick. No matter whether you swim freestyle or butterfly, you will/should still use the dolphin kick to keep the momentum off the start going. The kick itself comes out of your sternum and continues in a whipping like motion down to the tip of your toes. Note, I said the kick starts in your chest. This means that your arms, head and shoulders are totally still in a tightly integrated streamline and are piercing through the water like a javelin would. This is very high level, so more on dolphin kick in a different post.
5) Powerful and smooth breakout - After a great underwater work at the right depth and for the right time you are ready for a breakout. Breakout is the act of coming out of the water to do some actual swimming of the stroke you choose. During the breakout, one would be tempted to do something similar to what is done during the dive clean entry where the fingertips pierce the water first and then the body follows. In the breakout, it is not really so, because you need to use your hands and arms for pulling, so they should never come out of the water first. Don't take me wrong, your arms are in a streamline, so they are leading you through the water, however, they don't actually break the surface of the water. Depending on your stroke, the first body part out of the water is either the back of your head and upper back (freestyle/butterfly), the back of your head (breaststroke) and your forehead (backstroke). During freestyle, you could even take it one step further and have your elbow break the water at the same time with the other body parts I mentioned. What I mean by that, is that you complete the first pull before you come out of the water. The pull actually pops you out of the water and then the recovery elbow could theoretically come out of the water first. So, one more time, imagine that you are using your arm or arms (depending if you swim freestyle or butterfly) to pull you out of that water. So your arm starts its pull right before any part of your body breaks the surface of the water. Is this confusing? This is actually quite hard to learn, because you need to judge the pull at exactly the right moment, so you don't add necessary drag to your body during breakout by starting your pull too deep. If you don't believe me, try doing a breakout where both of your arms come out of the water first and then try doing one where you start your pull right before your head breaks the surface of the water and then you be the judge of which one is faster. The fact is, if you let your arms/fingertips get out of the water first, you will loose the first pull, thus you will slow down from your burst speed after the start. One last important comment, KEEP YOUR HEAD DOWN and do not look for the surface. Pretend there is some object directly below your head on the bottom of the pool that you have to watch at all times and this will help you keep the head down.
Well, that is all there is to it :). As one wise man once said, "practice makes perfect", so get out there and keep doing starts, underwater work, breakouts until it becomes a second nature and you get it right.