I havent been lifting heavy for a long time yet but there are three tips i would give someone with less exp. than myself for the big three.
1.) When squat always keep the bar over your heels and bend at the hips first.
2.) On the bench bring it low and drive it home with triceps and leg drive.
3.) For dealifting you want to get as close to the bar as possible and just drive the heels through the floor while keeping a tight upper back