Check for chips, scratches, and abrasions (even if they don't appear to have penetrated to bare metal) and attend to them promptly. Clear nail polish will do until you can repair them properly.
Also check the frame ventilation holes if your frame has them (some frames have sealed and purged frame tubing and may not have these holes). Look for tiny holes at the top, bottom (or both) of your seat stays, chain stays, and front fork. These holes help your frame breathe and allow internal moisture to evaporate.
Use a pin or length of thin wire to keep them free of mud and road cheese.