To start, just use common sense. You need 1 of each color for the 3 gate cards and the 3 ability cards. So go through the ones you own and you can easily eliminate alot of the cards when deciding which to use. For example, many effect a certain type of bakugan or certain attribute. If you are not using that type or attribute for any of your 3 bakugan then that makes it easy to eliminate those cards and help narrow down your selection.Another great beginning strategy is to eliminate the use of cards that are dependant on your opponent or certain aspects out of your control. For example there are cards that require your opponent to be using a certain attribute or type of bakugan. There are also cards that require ability or gate cards to already be in someones unused or used pile. While these cards may be awesome if all the requirements are met, i would bet that more often than not the card will never get used. It is much better to have a card in hand that you KNOW you will get to use then to have a card that you may never get to use.These are just a couple of basic strategies, feel free to share your opinions on these or add to them.