When one of my young sprint athletes asked me about this I tried to think of a good analogy, so I talked to him about sports cars. You've taken your sports car around the Nurburgring in a time of 7.56 minutes (which would make you the 100th fastest) and now you want to go faster in the same car. How can you achieve this?
Start from the outside... Better tyres, or for you, better shoes! The sprinter needs spikes, the sportsmen need better boots and the cyclist needs the right shoes. Want to lift more in the snatch? Get a pair of weight-lifting shoes. In short - the right gear for the job.
Secondly - aerodynamics. A better spoiler for the car, a better body shape for you, or a specialist swim suit. Of course you can go to extremes, shaving your legs, etc. If that's what it takes then it has to be done.
Technique - the driver can practice and improve his skills, as can the driver, the sprinter, cyclist or swimmer. Get a coach, read, have someone film you and examine your technique. Look at what the top guys are doing, but remember their training programme is for them, not you. By all means use some of their methods, but use what works for you and put it together in a training programme.
Fuel - you have to put top grade fuel in the tank... You're not going to put standard unleaded in the car if you want to beat the track record. It's the same for your body, load it with the best food you can get, research it (what, when, how it's all prepared) - it all counts.
Rest (recovery) - if you keep pounding that engine too much it will start to go wrong, and the chances are you will have to keep spending time fixing it. Don't over-train, it can have a negative effect!
And when you've tried all of these tips, what more can you do? Unfortunately with the car all you can do is put a bigger, more powerful engine in. The same goes for you - to get more powerful (and therefore faster) you have to get stronger. Power is strength at speed. Research the exercises you are doing to make sure they're the right ones and perfect the technique before adding the weights.