The most common way to say "you" to one person is あなた (anata). This is the informal way to address someone, and it is used in casual conversation between friends and family.
To say "you" to multiple people, you can use the word みなさん (minasama). This is the formal way to address a group of people, and it is used in business settings, public speeches, and other formal occasions.
If you want to be more specific about who you are addressing, you can use the words 君たち (kimitachi) or 貴方たち (anatagata). 君たち (kimitachi) is used to address a group of friends or family members, while 貴方たち (anatagata) is used to address a group of people in a more formal setting.
Finally, you can also use the word あなた方 (anatagata) to say "you" to multiple people. This word is similar to 貴方たち (anatagata), but it is less formal and can be used in casual conversation as well.