I think you've gotten good advice so far, but what they haven't
mentioned is weight transfer as you move the board across the jointer
knives. Start the cut with downward pressure on the trailing end of
the board. This will rock the leading end up so that it doesn't touch
the knife until almost the middle of the board. Then, as you slide the
board across the knives, when the knives have been cutting wood for a
few inches, shift the pressure to the leading end of the board so that
the trailing end is lifted up. That way, you only cut the middle hump.
You should find that the board contacts the cutters for more of its
length with each pass. When you're cutting wood along the entire
length of the board, your edge should be straight. If not, your
jointer is out of adjustment or the board is too long for your jointer.
Having said all that, I find it easier to work the other edge - the
concave one. Run that edge over the jointer until it's straight. Then
remove the offending hump with a table saw as was mentioned in another
post. Or, If the board is not too wide, turn it on edge with the good
edge down and run it through your planer.
"Every man is my superior in that I can learn from him." - Thomas