Before installing my lift in my shop I did a bunch of research on placement and anchoring. I found a lot of information here and also called the company that installs and maintains the brand lift I bought, I bought a used Manitowoc lift.
I first mapped out the area availlable, with all the expansion joints in the floor. It's important to keep the mounting bolts away from any floor imperfections like cracks and expansion joints. Most lift manufacturers require 6", some 8". I have my 8"+. Then measure the biggest vehicle you're planning to lift and locate that in your drawing. Next figure out the width of your lift and the area on the vehicle that you are to going lift it at. This will tell you if you have the room to mount the lift. Also the space around the lift.
The location I had to mount my lift left me with abot 4 feet on each side and about a foot from my door and 4 feet from the shelving I have in front. I would have liked more but that's what I was left with. It seems to be enough room to get around my biggest vehicle, a '04 Dodge 1500 4X4 pickup with a four door cab and 8' box. The truck is just over 18' long.
This is the drawing I did for my lift location: