New Minor Forcing is a convention used to find a 5-3 or 4-4 major suit fit after a specific sequence of bids in which opener has rebid one notrump. The convention is triggered by responder at her second turn bidding an artificial bid of two of the unbid minor; it requires that responder holds five cards in the major she has previously bid and at least game invitational strength (11 or more points).
You can also use a New Minor Forcing when opener has rebid two notrump showing (18-19)points; now the responder needs only 6+ points and a 5-card suit to use this convention.

The purpose of New Minor Forcing (NMF) is to find a 5-3 major fit or a 4-4 major fit and invite game after partner opens a minor, you bid a major and partner rebids 1NT.

You give up the ability to play 2 of the minor partner did not open.  This costs very little, because when you and your partner have bid a minor and a major and ended up in NT, it is unlikely that you now want to play in the other minor.

You gain the ability to find a 5-3 major fit or a 4-4 major fit and invite game.

1. NMF is always the 4th bid in the auction and the 2nd bid by responder.
2. NMF only applies when opener has opened a suit, responder has bid a major, opener has rebid 1NT or 2NT and responder now bids the other minor.
3. You must have at least invitational strength (11+ pts. over 1NT)
4. You should be uncertain as to where to play the final contract and need more information from partner.

Yes. The bid of the new minor should be alerted as your partner may or may not have clubs or diamonds. All subsequent bids do not need to be alerted as they are natural.

 Opener's priorities are:

    1. Bidding a 4-card major
    2. Showing 3-card support for partner's major
    3. Bidding 2NT without either of those and a minimum or 3NT without either and a max.