Something basic aside from the rules.. like AA and premium hands are never a limp (well, almost never a limp, but it's never for beginner players), 72o is the worst hand in poker, of suit hands have worse
equity and should be played less, good players are the aggressive players, who often making others take difficult decisions, not the curious ones who play passive just "to see what's there next". That ATo is a pretty much a trash hand and is a lot worse than it looks like and so on.
It's hard to recall specifics really. It's many many basic things which cover different aspects of play.