At the Calc AB level there aren’t that many “rules” you need to remember (I think L’Hopital’s rule isn’t covered until BC, if I remember correctly).
Limits at infinity can be a bit tricky and you’ll just have to know which functions grow faster than others. For example, the limit as x → infinity of x^{10000}/e^x is zero, since the exponential function grows faster (alternatively, use L’Hopital’s rule).
Other times, you might be asked to compute the limit as x → infinity of P(x)/Q(x) where P and Q are polynomials. In that case, it depends on the degrees of P and Q.
Wait, there are tons of resources out there on the internet. You should be able to find at least some resources.