Here is probably the quickest easiest solution to most peoples razz misunderstandings. It was originally called, 7 stud low. The name has changed, the game remains the same.
This seems simplistic, I know. But it is amazing to me that when playing HORSE, and a quizzical newbie first encounters razz, and blows a whole hand or two, or three, cause he drew a boat, and lost, he then asks, typically '?????'. Several will make attempts at describing the game, but when I say 7 stud low, the lights usually come on.
Dave is right, razz is a bluffers paradise. The story is right there in front of your eyes, never mind that the bluffer has trips underneath. The game is simple in that the story is right there before your eyes, but the hidden cards are where the game begins.
Rule of thumb, tread cautiously with any starting hand with a face. You should be mucking any hand with a face in the first 3 cards. On occasion you will start A2 K or something else close to that. I sometimes take 4th street there, especially with a cheap card. I figure 1 out of the first 4 cards can be trash. BUT, do not get into a pissing contest with a face showing. A2 K-3, great deceptive possibilities, but what to do against xx 4-5, and the loose player who is betting aggressively? You know at that particular moment, he can not have a made hand, and you are looking good with great draw capabilities. Many would have folded at the K, I do at least half the time.
As for betting on 4th street. No one has a made hand at that point. To a savvy table, the up cards will make the decision for most of the players, and only good hole cards should continue. To a gamy table, you should wait till you have a way better than just good holding.
There are good primers in both Super System books.