1. 你好 (nǐ hǎo): This is the most common and versatile way to say "hello" in Chinese. It's a general greeting that can be used in most situations.
2. 您好 (nín hǎo): This is a more formal way to say "hello" and is used when addressing someone older or someone in a position of authority. It's similar to saying "good morning" or "good afternoon" in English.
So, if you're unsure which one to use, "你好" is generally safe. Just remember to use "您好" when you want to be more respectful.