How do I tell if my roof is damaged after a storm?

After high winds or hail, immediate inspection prevents small damage from becoming large problems. From the ground with binoculars, scan for obvious gaps where shingles are missing. Look for shingles that are bent, curled, or discolored differently than the rest.
Check gutters and downspouts for shingle pieces and debris. If gutters are full of granules (the gritty coating on asphalt shingles), hail or weather has stressed them. Check your yard and neighbors' yards for shingle fragments.
Close inspection
If safe and the roof pitch allows, climb a ladder and walk the perimeter. Look at flashing around vents and chimneys; hail dents metal. Check for cracks in shingles or missing seals. Take photos of anything suspicious. Your insurance company will want documentation.
Documentation for claims
Photograph all damage clearly, including close ups and wide shots showing the roof section and your house for context. Date stamp the photos. If damage is extensive or you're uncomfortable climbing, call a roofer for a damage assessment. Many offer free inspections after storms. Document their findings for your insurance claim. Don't delay; some policies require claims within a set timeframe after the event.