I act as a personal trainer for my wife, but generally I am through most of my workout by the time she gets to the gym and am just doing some small finish work in-between her sets.
As for me training with a partner, the only day I have a lifting partner is bench day. When you bench heavy always have a spotter. Sometimes though it is hard to find a partner that is lifting at the same weight and it does suck when you have to remove half the weight on the bar between your set and your partners set.