Hi~~~!!!!! I'm wondering does anyone know any tips for Hetalia RP?

Oh, I'd love to help you out on that!
Haha...I hope this doesn't come off as bragging, but...I've written two articles on here that may help you.

Here's an article you can read about each of the characters' personalities: link

And here's a guide to Hetalia roleplaying and what you should and shouldn't do: link

I hope I helped! ^^

you have to act like they would:you have to focus on what THEY would say rather then what YOU would say, like:
SUCK IT LOSERS >:P

Try to make sure to act as a character would, like if your Canada be kind of quiet.

Another thing, make sure you're comfertable with whats happening in the RP....because once i was in an Rp with someone and they said and did somethings that made me very uncomfertable...so yeah......oh and Have fun