Opening 1 No Trump

An opening bid of 1NT is different from any other opening bid in that it shows exactly 12-14 HCP and a balanced hand..

Balanced means:
• no 5-card major
• no singleton (1-card suit) or void (0 cards)
• at most one doubleton (2-card suit)

♠ 32
♥ KQJ2
♦ KJ3
♣ Q632

1NT does not promise honour cards in every suit. This hand above is balanced even though it has two small spades.

Anytime you have 12-14 HCP and a balanced hand you should open 1NT in preference to 1 of a suit.

♠ A2
♥ AT2
♦ KJ932
♣ 632

You should still open 1NT with a 5-card minor, but not with a 5-card major.

__♠ A52
♥ KQJ2
♦ 3
♣ QJ632

This time you have a singleton diamond. The correct opening bid is 1♣.

♠ AKJ82
♥ J2
♦ KJ3
♣ 632

Now you have a 5 card major. 1NT is the wrong bid. The correct opening bid is 1♠.

♠ A2
♥ KQJ2
♦ KJ3
♣ Q632

This time you are too strong to open 1NT. Open 1♣, the lower of your two 4-card suits.

(from http://www.bridgeonline.co.nz/wiki/index.php?f=Opening-1NT-Acol)

Always make sure you know what your rebid is before you open.  If you don't know what your rebid is - should you be opening 1NT instead of a suit?  Remember you do not need an honour in every suit to open 1NT.