A good declarer relies on a variety of skills, strategies and techniques to help him make his contracts. One of the most basic is knowing how to handle common card combinations. You also need some knowledge of how long suits are likely to divide in the opponents hands, and you need to learn how to detect and use clues from the opponents bidding and play.
The most important of all declarer-play skills, though, is the ability to look at the entire hand -- all 13 tricks -- and develop an overall plan for making your contract. You should never just cash tricks randomly and hope youll know what to do later -- ideally, you want to have a reason for every lead and play.