Here are some suggestions for obtaining higher scores in Rock Rats.
The center of the screen is safer than the edges. You're less likely to get blind-sided.
During early waves, UFOs are not very dangerous. Take advantage of that to gain extra points. Don't get too carried away though, since they eventually get mad.
UFOs have a certain angular accuracy when shooting at you, so they're much more dangerous when they're close.
If you use headphones or have a device that can play stereo sound when in landscape mode then you can hear the direction of a UFO's approach before it appears.
Your energy reserve bar is green when you can jump twice, yellow when you can jump once, and red if you can't jump at all.
Shoot bursts at large asteroids and try not to leave small debris. If they're close, it may be better to dodge than to shoot and risk getting hit before you can react to fragments.
Prioritize small and fast-moving asteroids. Aiming at them is easiest when ahead but slightly to the side, and if you miss you're still safe.
Starting at a higher wave gets you a bonus that's comparable to the score from playing the skipped waves, and you do get a fresh three ships to start. On the other hand you can get at most one extra ship from the bonus. Some starting waves are better than others, in that after the bonus you may be closer to a score that's a multiple of 1000, which will give you yet another ship.