Probably the major cause of calipers binding is the metal 'ears ( tabs)' on the pads metal backing plate ( one at each end of pad that fir into grooves in the caliper ) are corroded and have jammed in the grooves instead of sliding freely to allow caliper to centralise around the disc. With the pistons only pushing on the inner pad the the pad on that side ( fixed side) needs to slide freely in its grooves as the pads wear, as does pad on the other side, as well the other side of the caliper needs to slide freely on the slide pins, but corroded ears were always the problem I found - ( other than once a split rubber gaiter had allowed water into slide pin and one had rusted). If you remove the clip-in shims from the grooves and clean behind them and ears are still tight ( they do not push in easily and slide, make sure you use hi-temp ceramic or molybdenum grease on the sliding surfaces) you can file 0.5mm off the sliding faces of the pads ears to make sure they go in easily and will stay free for the life of the pads.
you can get ceramic brake grease from motor factors like Euro car parts, I use TRW PFG110 brake grease on slide pins as it is rubber friendly and wont destroy the rubber gaiters like a petroleum based grease will, some pads come with a sachet of high temperature moly or graphite grease to use on pad ears and on back faces of pads as this is a much higher pressure area than the slide pins.
Don't be tempted to put extra grease down the holes where the slide pins live, they are blind holes and if too much grease gets in there you can get hydraulic lock where the pins are prevented from sliding properly, just clean out any existing grease and a smear of PFG110 or ceratec or similar ceramic grease - PFG is not expensive and I have used it for a long time without problems.