In order to really hone in on the "mind muscle connection", I like to tie a piece of string around the muscle I'm training. I do this first thing in the morning. All day long I feel the string and I visualize my rippling, striated, perfectly oiled muscles, contracting and blowing up from within. By the time I get to the gym that evening, as you can imagine, it's LIGHTS OUT.
*remember I'm one of the bigger guys here so this won't work for you if you are average.