What is the best way to get beautiful curls?

I have naturally curly, thick hair. It is just past my shoulders and layered. Don't get me wrong I love my curls :) but for special occasions or just for fun I would like soft, beautiful curls. I have tried hot rollers which don't work for my hair and sponge rollers which didn't do much. What is the best way to curl my hair? Should I use a curling iron? If so what brand do you recommend. Also do you know of any ways to curl my hair with sponge rollers? Videos would be nice also pictures, Please & thank you :)