The following excerpt is taken from the website: http://www.mysafefloridahome.com/three.asp
2. REPAIR THE SHINGLES ON YOUR ROOF Keeping shingles on your house is extremely important. Check to make sure they are well secured to the roof, particularly along the roof edges.
A common problem is that edge shingles are not well fastened or extend beyond the drip edge more than the 1/4” typically recommended for high wind areas. Once the perimeter shingles lift off, a peeling process starts and creates a domino effect.
The attachment of perimeter shingles can easily be checked by gently trying to lift the lower edge of the shingle. If it comes up without much effort (older shingles become brittle and may crack when bent too much), then you should secure them, which is easy.
If you find that a lot of shingles, including ones away from the edge, are poorly adhered, budget for a new roof in the near future. There have been significant improvements in shingles and the adhesive strips that anchor them to the ones below. New high wind rated shingles installed according to manufacturer’s recommendations for high wind areas and with extra edge sealing performed very well in the hurricanes of 2004.
Repair or replace shingles around any area that allows water to penetrate the roof sheathing. Leaks are particularly common around chimneys, plumbing vents and attic vents. To trace the source of a ceiling leak, measure its location from the nearest outside wall and then locate this point in the attic using a measuring tape. Keep in mind that the water may run along the attic floor, rafters, or truss for quite a distance before coming through the ceiling.
Use roofing cement in 10 oz. caulk tubes that fit ordinary caulk guns to secure roof shingles. It's inexpensive and one tube is enough for about 25 feet of shingles. Perimeter shingles include those along the eaves and gable edges, plus the ones on the ridge and hips. Place three 1" diameter dabs under each shingle tab (near the edges and in the middle). On gable ends, secure the three shingle tabs closest to the gable edge. If the roof is not too steep, an able-bodied person with practical skills should accomplish this in just a few hours.