The opening bid of one-of-a-suit is a very ill-defined bid. Basically speaking opening 1♣, 1♦, 1♥ or 1♠ shows roughly 12-19 points and that's about all the information you have. So the early rounds of the auction are a conversation between the opener and the responder, each trying to convey as much information as they can using the very limited vocabulary of the game.
Some of the "rules" for responder should be familiar to you - keep the bidding alive with 6 or more points but don't advance to the two-level without at least 10 points. We ought to say that keeping the bidding low is a sine qua non - the more bids you give partner the greater the chance he has of describing his hand.