If they're wearing a costume, it'll be super easy. "I love your costume! I'm Anon. Nice to meet you."

If they're not, you're already sharing a common interest by being at a weeaboo convention, so that's an INSTANT conversation starter, for guy friends and grills alike.

Just go for it man. If they hate you, you never have to see them again. If they like you, you've made a new friend. It's really not a bad situation.

get numbers and bond over shared interests

super easy to do at cons

anon keep in mind that socialization depends largely on the context, at least if you're bad at it

what I mean is that at something like a convention, a different level of sociability is assumed as compared to the workplace, the dmv, etc. if someone doesn't want to talk, move on. no big deal. just be mindful that your environment encourages it, so there's no need to feel self conscious

tl;dr Being social at a convention is normal and by not doing it, you can seem even more strange than by initiating random conversation

Wear a costume and people will come to you. If you are not wearing a costume, wear interesting fandom items. Consider the type of friends you want to make though. For example, I like Attack on Titan, but I wouldn't want to relate to them.
I once wore a Saint Seiya cloth pendant, and ended up hanging out all day with the 2 dudes who asked me about it. Choose wisely, and it will work out.

However, also remember that the sort of people you'll pick up are likely to be people who go to such conventions alone; they don't have friends. This is because they lack social skills and probably won't approach you to talk, and those that do will be autistic and creepy.

Also, OP, check if /cgl/ has a thread for the con you're attending )and feel free to start one if they don't). There sometimes are scheduled board meetings.