How to fix some skip frames?

Try activating the Frame Blending / Pixel Motion from the timeline Layer or from the Layer menu, that might help.

I'm not sure what you mean when you say there are a few skips here and there. Did the camera drop frames? Did this come from a render. Is the footage from a consumer device that shoots with a variable frame rate? Does the frame rate of the comp match the frame rate of the footage? 

If the frame rate of the comp matches the frame rate of the footage and you are getting a jump in the action then it might be possible to turn on frame blending, enable time remapping, set a keyframe on the last good frame, set another keyframe on the next frame, then select the second keyframe you just set and the last keyframe to keep that timing consistent and move the pair of keyframes to the right one or two frames and see if that helps hide the flaw in the footage. Try different blending modes.

We need to know a lot more about your project to give you any better suggestions than that.