~be sure you start with a new razor.
~shave in the shower, and wash your body first.. this will moisten the skin and make the hair softer to shave.
~exfoliate with one of those loofahs or puffs or something
~use a good shave gel
~ try not to go over the same area too many times, this will irritate the skin.
~after shower, rinse off and put aloe vera, or lotion
for the next few days be sure to keep exfoliating whenever you shower.
If it continues to be a problem, try using a cortizone cream (over the counter) to treat irritation.