There's nothing certain about what to do on each card, everything is situational - I couldn't tell you what to do on every card rank you receive because it is relative to the upcards of opponents!
But generally yeah you're looking to catch inside your 256. Normally you are going to the end if that happens, but if a guy obviously has trips that's not a hand you wanna draw against with a gutshot straight draw for pot sized bets and if he apparently fills up you fold unless you've made your low. I would say an 8 or 7
is a good card but not when someone has high trips. It's a speculative card to get - those cards get you in trouble when against other low hands.