Stuff I learned the hard way
1. Know how to fly your spaceship and have a plan for emergencies.
2. When you crash land on an unknown world, do not immediately go outside without protective gear.
3. Keep a low profile. Try to avoid smashing through walls or blocks of ice and uttering unearthly howls.
4. If possible, try to restart your ship before going on a rampage.
5. When attacking your prey, resist the urge to flail your tentacles randomly. While tentacle-waving is fun and good exercise, it leaves you vulnerable to sudden flamethrower attack.
6. Although everyone enjoys admiring destruction they've caused, it's best to destroy any evidence that you were ever there before moving on.
7. Don't assimilate intelligent life unless it's in a large group. Remember, the smaller the group, the more likely you are to be found.
8. If you're hiding in a small group of intelligent creatures, and one or more of them see you or your offspring, move on. They're not going to forget about you, even if you wait a couple of hours.
Follow these 8 rules, and you'll be on your way to galactic conquest in no time.