Another very important point. Never "double rotate" i.e. rotate to say 8 degrees and stop, then rotate to 15 degrees. When at 8 deg, the aircraft may leave the ground but will not climb more than a few feet. So there you are flying just a few feet off the runway then you rotate a second time, driving the tail into the ground. With a constant 3 degrees per second, as the angle increases the rate of climb also increases. This allows the tail to descend towards the runway at about the same rate as the aircraft is ascending. A win-win situation.
Know your airplane.