KNOW WHO YOU'RE PLAYING.
Jaina is a very squishy hero, so you want to slow your opponent as much as you can in order for you to get away and not die. You have to use blizzard as a skill shot and know where the other hero is going to be so you can be one step ahead. You want to use Cone Of Cold to get the crit hit one other heroes when you're accompanied by your tank and or healer in order for you to get that extra hit on them while chill is in motion.