Jacoby Transfer

After the 1NT opening the basic system use a suit on the 2-level as natural playing bid (except 2C if you use Stayman). This is an easy way to do it. 
With Jacoby transfer you use a transfer sequence to show a 5+ major suit. 
With 5+heart you bid 2D.
With 5+spades you bid 2H.

The opener should bid the suit above which is the responders major suit. 
(NB! Look at Accept Jacoby and Advanced Jacoby).

This method has two advantage:
1) The strongest hands get to play the contract.
2) The responder get another chance to bid.

Further bids:
There are three ways to bid after the transfer.
- New suit is invitational. (Not forcing)
- New suit is at least invitational. (Round forcing) The opener bids 3 in the responders major suit with minimum.
- New suit is Game forcing.

But these responses are the same:
1NT - 2D
2H - 2NT: Invitational. 5 heart.
3H: Invitational. 6+heart.