I will assume for now you know how Stud is played in its basic form and cover some of the basic aspects at a later time. For now, I want to talk about the “Lo” side of Stud Hi/Lo.
The same “Lo” rules apply to this as they do at Omaha Hi/Lo. That is, a low hand only exists in your hand of seven cards if five of them are values of 8, 7, 6, 5, 4, 3, 2 or A. On top of this requirement is that all five cards must be a different value. Pairs do not count, nor do suits and nor do straights. If you have 6h 5h 4h 3h 2h in your hand, you have a 6-high low which will be beaten to the low pot by anyone holding 6543A or 6542A or 6532A or 6432A or 5432A, whatever the suit. Of course, you have an almost certain winner on the high side with a straight flush.
The ace always counts low but only for the purpose of determining the low hand. The same ace can be used in the high hand too and takes its usual position, ie, it counts high for all hands except the 5-high straight (5432A) which is certainly a decent high hand but also represents the absolute nut low hand. Unlike in Omaha Hi/Lo, it is highly unlikely it will be matched and you should be able to see that for certain from your opponents’ up-cards.
This is the big difference in Stud - there are no flop, turn or river cards and therefore no cards to share with your opponents. Consequently, attaining a low hand in Stud Hi/Lo is not quite the easy task it appears to be in Omaha Hi/Lo. Your individual seven cards in Stud must contain five cards of 8 or less. There are 32 out of 52 cards representing cards from 8 down to A. Of those, you have to avoid any pair. It does not happen very often. Therefore, in Hi/Lo Stud, your opening betting should be restricted to the kinds of hands you would bet on in a conventional game of Stud except there is some scope for betting when you are dealt three low cards, ideally very low, connected ones.
Like Omaha Hi/Lo, there is a tendency amongst casual players to attribute too much value to chasing the low hand. In Stud, this is even more the case as your bets are likely to fail without upside for the high pot. However, a corollary of the reduced chances of completing your low hand using five of your seven unique cards is that, if you do hit a low hand, your cards cannot help anyone else. If they are to challenge you on the low side, they too have to receive at least five cards from seven, all of them worth 8 or less and of differing values. If you have a low, it might win even 8 high, which cannot be said for Omaha Hi/Lo.
Never forget though that you only ever win half the pot with the low hand.