What kind of situations would you use "sick" in to mean "cool"?

"Sick" to mean "cool" is most used among youth - particularly young males.

- When you're with your friends and you see a really flashy car, like a Ferrari, and say "Look at that sick car!"

- When you experience a really amazing roller coaster ride. After it, you could say "Wow! That was sick! Best ride ever!"

- When you experience someone doing an awesome performance of some sort, like skateboarding tricks or stunts or break dancing or musical pieces. Afterwards you could commend them by saying that that was sick.

In English class? I wouldn't bother.

If someone has a nice car, stereo, motorcycle, etc. you could say its "sick". Better to use the terminology to describe something that is high tech or cutting edge.