Crystal Maiden is a strong support espacially early and mid game, because of her good nuking+disabling combos. Use this advantage to gank early in the game.

At the beginning, in the laning-phase, you are with your carry on the lane. If he starts to get strong enough to hold his lane alone, start to gang and get your Team in a dominating position.

Place wards anytime. Your team is nothing without sight and you are the eyes!

Let's hope you have fun with CM ;)