Howdy,
Tactically, the first thing I do is sort my troops and add designations to the end of their names, as I did in old UFO... As the months go by and I'm given loads of cannon fodder (CF) soldiers, and a few occasionally good ones, I rotate them in to a squad or keep them on staff for injuries. I only really protect those with the ability to improve (at least competent Mind stat) and other abilities that are survivable, i.e. a high mind stat and a close with at least average speed... These are my SQ1 group, and if any of them die, I generally restart the mission, lame as that sounds. I also pick one of the SQ1 to be my kind of rep, high speed, average+ accuracy and competent mind; weapons skills are kind of bunk at that point. This member rocks the SMG perpetually... and I've had no problems yet, labeled OFF. Some of my SQ1 members are proficient or so in other weapons skills, namely Heavy Weapons, which somehow I lucked out and had two pretty good heavy weapons guys, a sniper, and a couple just so-so. The so-so-ers start with the plentiful shotguns (snipers occasionally), by the time I have better weapons they're strong enough in either assault or close to hold their own, provided they survive. Anyways, upon landing in the mission area, the first priority is to determine how F-ed the civvies are and how I can save them without taking too many casualties.
After a quick look around, I dispatch troops in pairs or so, sometimes more, depending on the situation. Often, I'll move my machine gunner or OFF to cover nearby building entrances (or windows, anywhere an alien could be lurking who could wind up with the drop on my squad next turn). I generally progress about the level aggressively with the light equipped members (namely the OFF, some CF, or whoever is closest to gunfire) but 90% of the time have at least one RF shot stored, about 50% the time multiple. All turns end crouched, most end near cover. I like to try to use the dropship for cover too, when possible, but on assault, the maps are forgiving enough to give you multiple firing arcs to cover your soldiers. Windows are great.
I have noticed, however, that my soldiers have a very hard time responding to fire from a higher level, like in the Estate map, even my Sniper. Maybe they just don't have an angle to see the enemy.