There are several things that I have learned over the years to become a better player.
The most important of all is understanding the importance of position (IMO).
Second is probably patience. Mistakes I see other players make is playing too many hands, and wasting chips chasing gutshots and open-enders with hands they should have mucked to begin with. Limping in, then calling a raise with rags, then check calling with thin draws and middle or bottom pair hoping to improve. Calling when they are not getting the right odds
Next would be not playing scared when you do have the goods. People will often test you. A skilled player may try to outplay you with nothing.
And last but not least, learn how to range people. It is very easy. It is just a different thought process than some players have by default. Instead of just going with your gut, always think about what they could hold. By the river, sometimes you can have your opponent on a range almost down to their exact 2 cards. It is very helpful. Bad players are often transparent.
Just my $0.02