From Columbus, Italy's world renowned manufacturer of bicycle tubing, come these guidelines for inspecting your bicycle frame:

Every 1000 miles do a thorough visual inspection of your bicycle frame. Look carefully at any scratches or dings for any signs of cracking. Give extra care when inspecting the area around the seat tube clamp as well as the joint of the head tube and the down tube of your bike. 

Every 2000 miles redo the above inspection and take extra care while inspecting the area of the bottom bracket shell, the chainstays, and the front and rear dropouts. Also, inspect the integrity of the add-ons to the frame such as rack mounts, water bottle bosses, cable guides, as well as derailleur mounts. 

IN CASE OF ROUGH IMPACT, be sure to have your frame geometry checked by a high quality shop. 

Due to the extra abuse that these bikes generally receive, do your inspections at least twice as often as on your road bike. 

Do a thorough inspection the day before every race.