There are a few options in local dialects.
1. Y'all
Used primarily in the Southern US, this is a shortening of the phrase "you all," which is also used in its full form as a plural address. It may have been introduced to America by Ulster Scots immigrants who used the phrase "ye aw." Y'all also has a possessive form, as in, "How was y'all's day?"
2. Yinz
This one is a hallmark of the dialect known as "Pittsburghese." People who speak this dialect are referred to as "yinzers."
3. You-uns
Yinz originates from this form, also used in the Ohio River Valley around Pittsburgh. It's a shortening of "you ones," a usage that goes as far back as Chaucer.
4. You Guys
In the parts of the U.S. where they don't use "y'all," they use "you guys" instead, as shown on the map above.
5. You Lot
The "you guys" of Britain.
6. Yous/Youse
This one is found all over the English-speaking world, from Ireland to South Africa, to New Zealand, to New Jersey. It makes a lot of sense. How do you make something plural? Add an 's'!
7. Ye
When English had a plural form back in the Renaissance, this was it. It is still used in Ireland.
8. Super Plurals
Sometimes a plural is simply not plural enough. That's when it's time to pull out "yees," "all y'all," and "youse guys."