How can I line up objects in my project.

I created a piston for a training project. Basically it's a cylinder with two ends on it that are slightly larger than the cylinder. I copied the first cylinder and then modified it to have a larger diameter. When I copy and paste it puts it exactly on top of the existing cylinder. If I could only use my arrow keys to move the new parts up or down it would be REAL easy. Instead I have to drag them with my mouse and eye-ball them to line up. Yes, I have turned on front and side windows to help me line them up, but it sure is tedious when you start getting several cylinders in there (like an outer shell or a ring at the bottom...)

Is there anyway to constrain movement to one axis or move objects using keyboard?

Thanks,
Robert