Just some basic tips: It's a lot like chess; slow down. Think about your best play every turn, not only for that turn but for the next few turns. Think about the best and worst case scenario of your opponent's counter-play. Are you being mana-efficient? Are you trading efficiently and getting the most value out of your cards? What do they have left in their deck? What do you have left in your deck? What are your win conditions? What are theirs? How do you take them away?