In my quest to understand MySQL’s EXPLAIN statement and to learn more strategies for optimizing queries, I came across this excellent blog post from 20bits by Jesse Farmer:

http://20bits.com/articles/10-tips-for-optimizing-mysql-queries-that-dont-suck/

In summary:

1. Benchmark, benchmark, benchmark!
2. Profile, profile, profile!
3. Tighten Up Your Schema
4. Partition Your Tables
5. Don’t Overuse Artificial Primary Keys
6. Learn Your Indices
7. SQL is Not C
8. Understand your engines
9. MySQL specific shortcuts
10. Read Peter Zaitsev’s MySQL Performance Blog