RVs are so similar to houses in many respects that they require identical forms of maintenance. Seams around the windows, doors and on the roof, for example, require regular inspection and caulking on both your house and RV. The procedures for apply fresh caulk are also similar, with the exception being that a special type of caulking should be used in place of the normal household silicon caulk.
Inspect the areas around the windows (not the windshield), door frames, openings in the roof (like skylights), and wherever the sidewall panels of the RV meet. You will need a ladder for the RV roof, and should lay out a plank of plywood when you stand on the roof to do your inspection, since this will spread your weight over a greater area.
Pry out the old caulking with a putty knife. Some badly degraded caulk might be crumbling and need to be scrubbed out with a wire brush. Take all of the bad caulk out of the seam plus one extra inch into the good caulking, should there be any.
Fill in the roof seams where you removed only part of the caulk and all window and door seams with fresh RV caulking. Use a caulk gun, and apply the caulk with slow, steady pressure on the trigger.
Cover roof seams where all the caulk was removed with EPDM tape. Peel back the plastic film covering the adhesive side three to six inches at a time, and gradually lay and press the tape over the seam until the entire seam is covered. EPDM tape forms a better seal and longer-lasting bond that caulking.