Driving in mountains

Hey guys,
This summer I'm going on a holiday with my '91 Chevy Caprice wagon, pulling a trailer of 1500 lbs, and we are going to face a lof mountains. Some are pretty high. Any tips or do and don'ts when driving in a mountain area? I do remember something about not to use the lower gears to often or for too long time, bit I cann't find it.

I would bet the 1,500 lbs trailer will be accompanied by a full load in the car itself, and you have the 305 motor, right? I actually would recommend using 3 instead of 4 when hauling a load uphill at highway speeds. Even 2 on steep hills. It lets the engine rev freer and puts less strain on the transmission. And don't be in a hurry -- get in the slow lane and enjoy the scenery. Wind drag increases significantly at speeds over 50 or 55 mph.