If your not crossing any rotation axis's (I can't remember the plural for that) then use a target camera. You will find controlling the camera direction much easier.
Open the motion panel, click the Assign controller button and add path constraint. Then just pick your path. To control the speed of the path open up the graph editor, locate your path constraint and again add controller and pic bezier float. This way you can animate the speed, rather than being stuck with a linear curve.
If you want your caamer target to stay on the same path as the camera, repeat the above steps, but edit the keyframes so that the camer starts a little further down the path to the target and the target ends before 100%.
If you are set on using a Free camera, create a null and use a look at controller to control the camera direction.