The high five trick is just a variation of give your paw trick with a few minor adjustments :

1. Teach your dog to target your hand with his paw for a click and treat.
2. Present your hand as the target in various positions until you can hold your hand up, palm facing the dog with fingers towards the ceiling. Click and treat your dog for touching your hand with its paw.
3. Practise this until your dog is quickly raising her paw when she sees you put your hand up.
4. Verbally label the behaviour "High Five" when it is happening on a regular basis.
5. Add in distractions and work on having her do it with other people as well.

Sometimes you will want to use a different cue or hand signal than the one you started with when you are teaching tricks. There is an order that must be followed before your dog will perform the behaviour on the new cue. You must present the new cue before the old cue or the dog will not pay attention to the new cue.