Bringing something that the fans haven't really seen before to the table more often than not. Or bringing back something that they used to see but don't anymore.
Highflyers have the easiest time at it because in this modern WWE where highflying doesn't exist anymore, all a wrestler needs to do is a dive and the fans go crazy. Case in point: Justin Gabriel. He gets the best crowd reaction out of all the NXT Rookies because he does a 450 Splash. It's not even a good 450 splash. But because nobody has done one in a WWE ring in over 5 years he gets massive cheers.
Rob Van Dam was made in one night by unleashing 95% of his move-set on Jeff Hardy in a decent length match. The crowd went absolutely ape over the guy because damn near all of his moves had never been seen before. The wrestlers that debut for the WWE today are using the same recycled movesets, they have almost identical looks, and we're not getting enough diversity and difference. It's why I think Low Ki/Kaval will get massively over as long as he doesn't upset anyone backstage, his moves are massively different to anyone on the roster right now.
I have a theory that a lot of ROH, PWG or other Indie Wrestlers could get massively over if they ha the WWE spotlight shining down on them, a vehicle to deliver them to the millions. Not all of them, don't get me wrong, some are just trash, but there are definitely guys out there who would make a WWE fan's brain melt. The good, safe indie wrestlers are the ones that are inventing the new moves that work their way slowly into the mainstream, and when they finally get there the fans of either TNA or the WWE that see them pop like crazy for them.
So yeah, this isn't my greatest post because I've gotten a little distracted during it, but the point I'm essentially trying to make is that stars are made by being different to make the audience care about them. Kofi Kingston had a unique energy that made the fans connect with him, all the WWE needed to do is push him to make him a star, but they seem to have lost interest in that. Rey Mysterio wears a mask and does the 619. Jeff Hardy painted his face and jumped off things. Ted DiBiase and Cody Rhodes will fail to get over without significant work because they just look and wrestle like every other poor Randy Orton knock-off.
Want to make some stars? Dress them differently, have them talk differently, let them do different moves. Fans have a tough time getting into guys who wrestle 4 minute matches during which they only hit one real move, a finisher that they've seen a hundred times already.