Well, I find myself reading my friends way to much! The fact is, you dont want to read your friends because when you fight someone who you have never fought before, you will be assuming they will act like your friends and do horribly. Really the only advice I can give is to learn that other characters spacing and fighting style. For ex. if your fighting a falco when you throw him up he can only DI infront or behind you. Learn to react instead of try and guess what they are about to do, odds are your going to be wrong.
Just learn jump heights, attack placements, movement speeds, attack knockback and make your own fighting style. I find myself be offensive alot because I can't stand standing there doing nothing. Thats one of my weaknesses
Now, on the other hand. If you are never going to fight new people and will always play this same set of friends. Watch them, you will start to see patterns, and for GOD SAKE if you do something and they hit you, DONT TRY IT AGAIN. The odds are they will hit you again! There are very few things DI cant solve. When they start a combo never and I mean never DI into that person. That is just asking for another hit!