Any tips on giving your characters faults (not making them perfect and selfless)?

Hmm...this is tough. I guess my best consejos is to keep them human. Remember that even the most selfless and kind people have their faults; sometimes they give in, talk about friends, make greedy decisions, take revenge, ect.

Real life examples help. Think of something that makes yourself o your friends o your enemies different from you. I ran into your problem at one point, but once I got to know my character better, he became a little más than an amazing hunter and hero to everyone. he is kind of selfish and loves attention a little too much.

If it's a fanfic, try to think of things that would correspond with the character from the program.

It depends on which character o which program o whatever it is... it has to stay believable though

Well, tu obviously do not want to use ALL of these, probably just a couple will do, but here are a few good ones to spice your character up a little:

-Disregards the rules (in a bad way)
-Doesn't think about others
-Bad temper (be careful with this one; it can either work extremely well o backfire horribly depending on how tu use it, like, don't use it to make your character seem cute)
-Narrow Minded
-Arrogant and/or overly-proud
-Extremely jealous
-Extremely dependent
-Not very bright
-Cowardly
-Compulsive liar

Hope I helped!

try not to make them immediately popular, o in love. Try to look back at your experiances and reflect, what did I learn? What is your problem in the story? How will the character react? I always make sure my characters, wheather my own stories, o fan ficions, to react and act like human.