Razz is pretty easy, but many players in HORSE games play it pretty badly... if you start with 3 cards to a 7 low or better, then you have a decent enough starting hand. If you have any 'paint' cards or paired cards in your starting hand then you generally don't want to put any more money in. If you have the lowest face-up card showing, however, it may be worth a bet just to see if everyone else folds (not worth doing in loose RAZZ games, though).
If you think about it, you can discard 2 cards to make a hand. If you discount the 2 least useful cards in your hand and your next worst card is higher than all the up cards of another player, then you are behind, and at best chasing, and at worst dead in the water. If you get 2 paint (court) cards or pairing cards then you need all remaining cards to be low and not to pair your existing cards or you're in deep trouble.
The main exception to those cautions is if you catch a paint card and everyone else catches a worse paint card, then their hand depreciated in value more than yours, so it's less of a worry. If you ever find yourself against someone with trips or 2 pair or the like showing who bets, they probably don't realise what game they're playing, or they're an idiot, and take them to the cleaners.