Need tips on getting rid of Rats?!

I have some rats around the shed and they have started to knaw on the wood and have somehow gotten in my pigeon shed and have left there dropings around there is a little hole that goes under the shed so I geuss there living under it now. :rolleyes:

I blocked off the main entrance they made to go into the shed but somehow my mom found dropings & last night I went outside and I seen a huge rat run by me No im not scared of them I just dont need them around.
Rat droppings can make a bird sick and some rats carry a sickness so I Do not need these guys around at all.

Any suggestions on how to get rid of them?