Sooner or later, no matter how careful you are, you are going to get a hole in your kite's sail. Of course this is a bad thing, and something to be avoided, but when it happens you can usually fix it yourself and the kite flies without any problems.
If the hole is only a couple of centimetres then you can use special sail repair tape - in my case Flexifoil kite repair tape - to tape over the hole. For larger hole, or rips some fabric needs to be sewn over, or part of the sail replaced. Contact a good kite shop to talk about costs of larger repairs (note for Flexifoil kite owners - Flexifoil have a repair service on their kites, so contact them).
And that's all there is to it! Simply go and fly your kite. Using the clear tape I find I don't notice the patches when flying as I have to be 'up close' to see the repairs.
I have repaired 4 kites this way (the C-Quad, Obsession, Revolution 1.5SUL and Flexifoil Fury).