Get yourself a straight key, code-practice oscillator and a sound-card-based CW decoding program for your computer.

Hook the output of the oscillator into the sound card's input, fire up the key and practice sending.

Watch your progress on the monitor.

If you don't get the character spacing exactly right, the character elements are going to look like a bunch of random "ees" and "tees" scattered across the screen.

This is a good technique to use when developing timing with a hand pump, and you'll also find that it will help you copy better when on-air.