when lining up tracks for editing( aligning 2 or more ), how much should I be zooming in ???

How did the tracks get out of alignment?

You can zoom up to 1 sample however as small I ever really go is 128 samples. Make sure snapping is off so you can be precise with the adjustments. Essentially the easiest way is to snap to the nearest bar or interval. Then any differences after that can be fine tuned. 
 
This is how I would do it anyway.