[kurttruk820]

You can place limit switches at the extents of your life travel (i.e. top and bottom), but make sure you pair them with a hard stop that will prevent switch damage.

Also, since the lift motor won't stop exactly when you hit your limit switch, it's always a good idea to build in a mechanical fuse/damper somewhere along the lift chain. A simple solution would be to terminate the lift chain on something compliant, like a spring, so that if the motor keeps rotating a short time after you've hit your limit, the spring will stretch instead trashing the motor or bending something on the frame.