1. Check your anti-virus settings
2. Be conservative in your diagnostic logging settings (think
warning/error)
3. Check your IIS logging, turn off if not needed
4. Turn off trace logging unless troubleshooting
5. Check your usage analysis settings
6. Don't full crawl unless you need to. Just incremental and check
schedule
7. Turn off Doc Conversions and ECS if you don't need them
8. Prune back site collection auditing if you don't need it.