1. Don't be afraid to try new ingredients.
2. Don't boil for under 45 minutes (no matter what the recipe says).
3. Don't add the malt extract with the brewpot on the burner (you may scortch the malt).
4. Don't open the fermenter during the first few days of fermentation.
5. Make sure the fermenter, bottling bucket, and any other equipment used in the process is sanitized well!!!
6. Don't add too much sugar too when carbonating the beer.
7. Leave a minimum of 1 inch head-space in the bottles.
8. Don't worry if the first few batches don't turn out so well. They will get better with time.
9. Finally, never never take brewing too seriously. It's only a hobby and it should always be fun.