Just be yourself. A lot harder than it sounds i know, believe me i know. But as someone who has pretty much always hung out with dudes take it from me. They are a simple species. If you are into something considered “geeky” let it show (yugioh, star wars, transformers, video games, anything.) If you find dirty jokes to be funny, use them. If you get shy, who cares. If they’re worth your time and effort they’ll appreciate your little quirks and flaws that make you who you are.
And if one of them pass an insult to try and embarrass you, throw one back at him. Trust me. I speak dude. It works.