First, get to know the birds habits. Kingfishers will use the same perches over and over. They have a territory they prefer and they will travel from one end of it to another, usually using the same vantage points. They only eat fish, so they want to look down into the water from a branch or wire over the water. Look for them there.
They are very skittish and don't want you to get too close, so if you are still scouting the shore or bank, look out ahead. If you see one already in the air, try and watch till he lands and maybe where he came from. Stop where you are and settle in for awhile and he may eventually come back near you.
Some people use blinds and have even put up a stick or log over water that the bird finds convenient and will use, while their blind is set in a spot to shoot the log. I have found a spot they seem to like in a tree in our wetlands and just stood in the open with my tripod and had the bird come within shooting range before. As a kid, we had them fishing from branches right over our swimming hole in the river, sitting there and diving in right beside us while we swam. Go figure. These birds do what they want.
For shooting them, I use AI Servo and high speed burst mode. Your IS lens takes up to one second to spin up, so maybe turn IS off if the light is good enough for high shutter speeds. The birds often hover over water while waiting for a fish to show itself, so be ready for that too. If you find a favorite tree, stake it out and don't move around much and they will eventually come back to it. It helps to be already aimed and focused on the branch they prefer.