Determining How High to Bid
The number of tricks your side can take correlates strongly with the number and rank of your high cards. To make game in notrump or the major suits, you and your partner need about two-thirds of the high-card strength. That means that you should open the bidding when you hold one third of the strength. If you pass with that much, you run the serious risk of missing out on a game contract that can be made.
The simplest way to express the difference in value among the high cards is with a scheme of rating points, assigning a value for each honor card. Note that assigned points for high cards have nothing to do with scoring points. It's like rating baseball players on a numerical scale, with the weakest player rated at one and the strongest player rated at four.
Starting with the lowest, you count one point for the jack, two for the queen, three for the king, and four for the ace. Each suit contains ten high-card points, and the whole deck contains forty. The two-thirds requirement for game translates to 26 points. So, if you hold 13 points, you should open the bidding. If your partner opens the bidding and you hold 13 or more points, you should guide the bidding to game.
For example, holding 
A842 
KJ43 
KQ6 
94, you count four points for the Ace of Spades, three for the King of Hearts, one for the Jack of Hearts, three for the King of Clubs, and two for the Queen of Clubs, for a total of 13. So, if you deal, or no one before you bids, you should open the bidding with this hand.
