Generally,the front edge puts the lighting over the center of the counter where you are working. If you are using pucks, they can go in the middle as well, because they cast light a bit more evenly, kind of like a recessed can.

Some people mount them at the back. It also has to do with how reflective the backsplash is and whether "hot spots" bother you and you want a more even look.

I've had front and back mounted - I prefer front - lights up the entire counter workspace better.

Front or center, or it will not lite up your backsplash well--had a friend that did them in rear and redid them to better lite the backsplash.

Gary

For best functionality, definitely front or center. Will also help to keep them out of view from a distance.

I have them placed in the back, but I like them more for ambiance (and lighting the backsplash) than for task lighting.