Trimming corals question

[Darth Wader]

Hello everybody. I have a quick question for anybody who is willing to give me an answer or even just some suggestions.
I have a fairly large colt coral and a few other soft corals that I think I will need to trim soon. They seem to be growing at an unbelievable rate. I have read that people do this when corals get to large. My question is how do you trim the coral? I dont wanna hurt it and end up killing it. If anybody knows how to or has any tips on how I can trim it down let me know.
Thanks,
Darth Wader