Versus a strong NT: Bid when you feel like it, the main purpose is to get to a part score. Still, 2-suiters are at least 5 - 4. 2-suited double applies.
Versus a weak NT: We want to find a good contract. Bid constructively. Penalty double applies.
Here are the responses to the opposing 1NT:
/
and 5+card minor
:
+
. Partner bids 2
to ask for the longer major.
:
or
. See Multi for continuation.
/
: 5+card and 4+card minor. See Muiderberg for continuation.
+ 
: Pass or correct
: Bid your major
/
: To play