The opening hand. When you collect your initial hand, whether it is through the standard nine-card deal or picking two and then discarding, the opening hand is important. If you only play the standard method, save yourself some time and then skip on to the next step. The booster packs introduced the variant method for dealing. What to keep and discard.
Warheads are always worth keeping and the same goes for missiles.
Most special cards are worth hanging onto, with a particular preference to the anti-missiles. Now you have your nine cards. Place two face down cards and then place a missile for the third. My reason is simple, the cold war strategy in the rules may work, but I have never seen it, I think this may be down to the weighting of the game to missiles and warheads. First and subsequent turns.