Let's start with the most obvious one: Play fairly.
Don't cheat with walkthroughs and suck, it only ruins the fun.
All answers will be in lowercase unless specified.
Sometimes a Google bar may appear below the image, implying you need to do a little research.
(for the first 10 levels)
1. It's on the image.
2. It's easy as ABC!
3. Listen to what I say...
4. Control yourself!
It's Danish port salut, but backwards
6. I could really go for a Ceasar salad right now...
7. Get your scanners ready!
8. Hexes can be handy for more than just UTF-8, you know.
9. It's not level 8!
10. Rainbow order.