M J Bridge
Theory and Conventions
Opponents opened one of a suit
It goes more or less without saying that this is the bread and butter situation of competitive bidding.
There are all sorts of approaches.
The important thing is that you and your partner are agreed on what is promised by a raise of a suit, what various support bids are available, and what is promised by a bid in a new suit.
Beginner and above
Advancer’s first bid