Poker is a game of incomplete information.  But in 7-stud, that information is a lot less incomplete than in other forms of poker.  At a full 8-man table, you get a lot of information on your hand's possible future before you have to make your first decision, and whether or not your cards are "live" factors into this and every decision you make thereafter.

A card being "live" means it is unduplicated in your opponents' boards.  So if I had a pair of split Queens with a Ten kicker and no Queens or Tens were showing, I would say my hand was very live and I could play it aggressively if noone had an open Ace or King.  If a King raised and I was faced with calling a raise with my Queens, I would throw it away every time--unless the Kings were "dead" and my Queens and my kicker were completely live.  If there were 2 other Kings on board, I can figure my opponent's chances of improving are slim while mine are good, and I might continue with my hand.

On every street you must continue to track whether your cards have remained live.  With those same Queens, if someone with a Jack door card hits an open pair of eights to go with it, you can continue only if your Queens and other cards remain live.  If they have fallen slightly dead and it looks like someone has made a low to boot, you'll have to fold to the obvious two pair.  

For the low hands, you want to look for the low cards that will fill in your straight.  If you're playing well, you'll be avoiding the razz hands, and only playing the lows with a possibility to scoop.  I won't play an unsuited 862, but I will play the 876.  The first makes a better low for half the pot, but the second has a shot at the whole thing.In 7-stud Hi-Lo you need pretty strict starting requirements, so let's see how live cards affect them.  

Rolled up trips --

Live or dead, it's only one card.  The time to check for liveness of this hand is as it develops.  If someone gets a very scary flush or straight board and all your kickers are dead you can get out.  Otherwise you're usually going to take this to the river unless you're very sure you're beaten.

Baby straights, suited and unsuited --

I will almost always play these, regardless of liveness, giving extra juice to the suited hands.  However, if the cards are very dead and there is appreciable action from other baby cards/aces, I would be forced to let it go.  If they are only slightly dead I'll play them soft, calling and letting the hand go if I catch a bust on fourth street.  In fact, it almost always right to fold fourth street if you catch a bust card, except for the following: if I have a premium low starting hand with live cards I will raise and reraise on third street.  This builds a pot big enough to give me the odds to continue with the hand if I catch a bust and my cards remain live.  You must continue to reassess the liveness of your hand. On every street I am always thinking, "Live, price, and possibility."  Are my cards live?  Am I getting the right price to call/raise?  Is there possible action behind me?

Aces with a low kicker --

Again, nearly always playable even if one of the aces is dead.  If it is live, I will go to war on most streets until my low possibility has completely died and I haven't caught a second pair.  

Aces with a high kicker --

I'll play it fast to get it heads up, but if my cards are dead or die along the way, I'll switch to check and call mode to try to get to a cheap showdown.  Might even fold it if my opponent is freerolling or catches an obvious trips or two pair and my cards have died before the pot has grown enough to justify chasing.

Three low cards with an ace --

This is a hand I like to play fairly fast if my cards are live--very fast if they are suited and the flush is live.  It can turn into a very big hand and if it does, I want to win a pot to match.  Additionally, if the ace is up I can occasionally represent a pair of aces and win heads up against a low if we both catch busts.  

Best high hand on board --

With the 8 qualifier for low, high hands become playable.  But you must be sure you have the BEST starting high hand.  You don't want to draw second best for half the pot.  The only exception is if your hand is VERY live and your opponent who has you beat has a very dead hand.  These hands must be live regardless, as you're unlikely to fold out someone with a low draw and you need to be able to survive if they back into two small pair.  If they catch a suited baby and their cards are live, I tend to fold fourth street.  If they catch bad I'll fire until they look like they're free rolling or my cards die.


Three-suited low cards w/o an ace --

If the flush is not very live then it must be the best low working.  Otherwise, despite how pretty it is, I'll play it soft and be ready to release if it doesn't develop very quickly.


8 high straights, gapped straights 8 and under --

These need to be very live and the price needs to be right.  If they're live I'll call a raise with them, slightly dead and I'll limp if I can close the action or am pretty sure that there won't be a raise behind me.

Three-suited cards, two of them low --

The flush must be live and the price must be cheap.

Razz hands (unsuited and completely gapped low cards) --

These are unplayable unless they are very live AND the only or the best low working.

Low Pairs with a Low Kicker or low pairs with an ace --

There is a big difference between the ace or the low kicker, but neither is playable unless they are completely live  i.e. neither the pair card or the kicker is duplicated on board.  The good news is that these hands have some built in deceptivity about them, as they can develop into very good high hands while looking low.  

Three cards to a consecutive straight flush --

As this hand has so many outs to a very good high hand, it is actually playable despite not being in the lead for high right at that moment.  But, of course, it must be live!

Most other hands are unplayable unless your hand is very live and you can close the action down.  I won a very big pot once with a 987 offsuit because I was last to act and all the 6's and 10's were live.  With the 7 up, the 10 I caught on fourth street looked like a complete bust.  The pot was still multi-way, so I was looking at a whole bunch of cards and none of them were 6's or Jacks, so it was a no-brainer to stay in despite some appreciable action.  Ended up with a ten high straight and a rough 8 for low and scooped.  Still, you must be very cautious with this kind of behavior.  Even live, a split pair of fours with an unsuited 9 for a kicker isn't going to play real well.