One good way to flirt is to have a prop that attracts attention.
Big watches, funny hats or anything else that is distinctive are all good options. These will make people more likely to approach you because they are intriguing and will also give you a good topic of conversation for when they do approach you (or you approach them).
Whispering is a good flirting style because it creates unexpected intimacy.
If you tell someone you need to tell him a secret, then get really close and whisper in his ear, he will feel extremely close to you as you will be literally close to him. What's more, he will feel your breath on his ear, which he will likely find enticing.
Complimenting someone from time to time is a good flirting style because it shows that you're taking notice of -- and approving of -- various elements of her style or personality.
So, show a little more flattery than you would show to other people, and it will likely be very well-received. Just don't overdo it, because that will make you seem desperate for approval.
Open-ended questions encourage listening over talking.
Most people positively love talking about themselves with someone who is interested in what they have to say. So, if you ask someone open-ended questions and listen attentively to the answers, asking more questions to encourage him to keep talking, then he will likely become more interested in you because you are such a good audience.
Touching someone is a good nonverbal way to flirt with her.
By leading someone through a door, touching her arm when she makes you laugh, or patting her hand in consolation, then you will be showing her that you're interested in her. Friends don't touch one another particularly often, so if you are touching her a little bit (but not too much), you will be making it clear that you are interested in her.