"Skip-Bo" is a very challenging two person game that you play with a "Skip-Bo" deck of cards. "Skip-Bo" is also a game that you can win every time if you stick to this strategy. Here is how to win at "Skip-Bo" every time.
Keep your "Skip-Bo" discard piles clean. You will have four discard piles to discard to, and you want to keep them from largest to smallest. Generally you should keep two piles for like cards, and two piles for numerical ordering.
Play to advance your "Skip-Bo" hand and not to block your opponent. Most rookie "Skip-Bo" players spend more time blocking than advancing. The object is to clear your deck first, so advancing should always take priority over blocking. If you can block without preventing yourself from advancing then go ahead.
Watch your opponent's discard pile. You can generally make out what your opponent is trying to do by watching this pile. If they are trying to reach a seven for example and have 1-5 on their discard pile, then their is a good chance that they are looking for a seven. Use this to your advantage when possible by playing yours first and thereby preventing him.
Utilize your "Skip-Bo" cards very carefully. Do not just use a "Skip-Bo" just because you have one. Save it for that run of cards that you need to get to your next card. "Skip-Bo" cards are valuable and should be used to actually advance your deck, not just to plunk down some cards.
Know your opponent when you play "Skip-Bo" so that you can capitalize on their mistakes. All "Skip-Bo" players have a style. Whether it is an aggressive style or a conservative style you can play off of that by knowing. If they are aggressive take a bit of a passive approach to your game play.
Always save your "Skip-Bo" cards for your extended play. Always play the cards that will get you a new hand when it is available.
Never block someone at the expense of you advancing your hand.