At anime conventions, there are boatloads of cosplayers. Sure, I'd still only guesstimate that 30-40% of con goers at any particular con is in a full cosplay, that still means thousands of people in most cases.
So how do you make yourself stand out?
1. Choose an Unknown That Everybody Knows
This may sound impossible, but this is the way to make everyone that sees you on the con floor stop and go "Oh, damn!!!" Choose a character or bring a meme that everybody knows to life.
The crowd will be more impressed if you pick a costume no one else even thought of!!! And for that reason, I can't tell you exactly what this is, but think out of the box in regards to funny nerd-dom, and you'll be on your way.
(One example above: the box from Metal Gear Solid. Not everyone is going to get it, but a lot of people will....and they're gonna love it.)
2. Pay Attention To Details!
On the left is a cosplayer that went with a really, really popular and intricate outfit but didn't stand out as much to me because they lacked the necessary details. It still looks great (and I think it was probably WAYYY more affordable than some other Lulus...), but compared to a Lulu cosplayer with more intricate details, it doesn't stand out as much.
On the right is a cosplayer who chose a generally more simple outfit as far as construction goes, but by including everything (like alllllll the boy scout badges and the balloons!), really stood out as an awesome cosplay!!! Russell from UP is also just an insanely cute idea to try.
The key is this: whatever you choose to do, make sure you include every little detail that you can!! Seriously!
3. Be Funny
As someone who isn't naturally funny, I'm really not the person to be giving out tips on this. But any time that you can be funny with your cosplay, you're going to get a lot of points with other con goers!! And like 10x more pictures. And you might get to be internet famu. But I can't guarantee any of those things.
Example: I've used this one before, but I still think any PokeBro is a hilarious bro and thus I am going to use this as my funny cosplay example until the end of time.