For starters this is best suited for a character specific forum. Secondly, it's way, way too vague. What character do you use? What characters are you wanting to edgeguard better/struggle against? What are your common strategies that you use to edgeguard, and etc.
Without knowing more about you, nobody can help you. I can give you some really solid advice about edge guarding, but more than likely you wouldn't understand it in a way that would improve your play because you aren't at a point at which you could make use of the advice I give.
I'll give it anyways:
Edge-guarding is all about positioning and eliminating the options your opponent has while he/she is off the stage. Your goal, obviously is to keep them off, and not to give up your advantaged position (that being that you are in position to KO them). So you should be patient and react to what they do, or use an option that still gives you the ability to cover other options later (such as taking the ledge and waiting for them to respond to the fact that they cannot take it themselves).
You also have to make sure you don't put yourself into a position in which you over-extend, which means you have to have a good understanding of your opponent's character and their options in order to apply pressure but not giving up your positional advantage. Often times newer players get greedy, and go for a risky play that is usually quite obvious. This is bad, because more than likely what happens is that the greedy player loses his advantaged position and is immediately threatened with edge guards themselves.
