SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

Have a sprinkler head that will not pop up and spray. But don't have much experience with sprinkler systems. Can someone please give me a few instructions on how to go about fixing/replacing sprinkler heads? Or point me to a website that can help?

Do I need any special tools?

The heads are a mixture of Rain-Bird and Hunter.

Thanks.