When playing heads up, you should play more aggressive, as the best hand heads up is usually weaker than 6-max or 9 seated. And this is because less hands are dealt. So, I recommend that you raise preflop often, even with relatively weaker hands, such as 7-5 rainbow (usually low bets/raises, such as min bets). With these hands, almost always only raise preflop, like when you SB (small blind). When people allin a lot, try to get a pretty good hand, and let them shove on you. I recommend that you don't shove low pockets (like 2s-7s or something), as there is probably a good chance that the hand ends up with a coin flip. Pocket 8s and up are better, as you have a better chance of having at least one over (one of their cards lower than yours). Now, when you don't have pockets, something like 98 suited and up is a reasonable call allin. Obviously, its your cards and money, so you get to make these decisions, so you decide what you allin with. You can look at an odds
calculator to see how certain hands match up with others. Have an amazing day! Plenty of them!