I was taught to joint the concave edge first, if you have a long enough jointer table. If not, then the following is how I was taught to do it, on the convex edge first:
Assuming the crook is centered on the length of the board, put the center of the board edge down on the infeed table (power off), and slide it toward the cutter head until it almost contacts the cutter head.
Now clamp a shorter, straight board to the face of the board to be jointed, with the straight board's edge down flat on the outfeed table. This will hold the board steady lengthwise for you while you make the first jointing pass, to create a flat spot. Start this first pass with the cutter head between the end of the short, straight board, and the peak of the convex edge of your board, such that the cutter is not contacting the bottom of your board until you slide it further over the jointer. If the resulting flat spot is not long enough for you to hold the board steady on it without the clamped board, run the entire length of the clamped assembly over the jointer again, until the flat spot is long enough that you no longer need the straight board for support.
Now you should have a flat spot on your not-yet-straight board, long enough to allow you to joint the rest of the board straight. Remove the other straight board, and finish jointing, keeping the flat spot down on the infeed table (and outfeed table as it passes over the cutter head). The flat spot should keep getting longer until it covers the whole length of the board, then you are done.
It may help to draw a straight line along the face of the board, next to the convex edge, especially if the peak of the crook is not centered on the board. This can be used as a guide for clamping the straight board, such that this straight line is parallel to the jointer tables.