In Spanish is it sometimes awkward when deciding to use tu or usted?

You use tu for all your friends and family. As for people you don't know as well, you should say usted. To answer your question, they will probably tell you when you can use the tu form with them. Using the tu form has its own word in Spanish "tutear." You may hear something like, "Ahora me puedas tutear cuando quieras," or something to that effect.