Things I learned in the last 5 or so years
Here, learn from my mistakes!

1) It's cheaper and easier to buy someone elses sound library.
2) Sometimes, advertising really works.
3) Web templates are worth the money.
4) Portals don't have any success with strategy games.
5) Leaving error checking code in the game is well worth doing.
6) Turn based games are easier to make.
7) Always check your royalty statements.
8) Sometimes it's ok to raise the price.
9) Mock up everything in a graphics program first.
10) Big games developers are staggeringly inefficient.
11) Big games publishers are often totally incompetent.

Save game code starts today. *shiver*