1. Use an SQL Injection Cheat Sheet
2. Know the Difference Between Comparison Operators
3. Shortcut the else
4. Drop those Brackets
5. Favour str_replace() over ereg_replace() and preg_replace()
6. Use Ternary Operators
7. Memcached
8. Use a Framework
9. Use the Suppression Operator Correctly
10. Use isset instead of strlen