The game itself has a lot of information in the Bootypedia about controls.
I think an important thing to note is the important of captives and the validity of melee combat. A lot of your research and money comes from interrogating, selling, robbing or enslaving captives you take, of which generally the easiest way to obtain is run up and batter unconscious with Daze or Electricity-type weapons like the handle, stunprod and cattle prod. Most early firearms are pretty trash, to be honest, so for tough enemies a strong gal with a sledgehammer or axe can often do a lot better.
Units trying to shoot while adjacent to the enemy have to beat the enemy's evasion score, or their shot will be diverted. It's easier to hit things - melee and adjacent shooting - from behind, as that halves the evasion score of a unit. So running up next to an enemy with a gal with good evasion is a valid but risky tactic, as chances are good the enemy won't be able to shoot her (or will just trying run back anyway).
Your starting gals are good, and it'll be a while before you can freely buy more gals, so if it comes down to killing a potential hostage or letting a gal die, kill the enemy. There will be other opportunities. You can get the ability to hire peasants early on... but they suck. They really suck.
Your Gals have better vision than baseline humans, so a lot of the time night missions will give you the advantage. For some enemies, though, like ratmen and reticulans, the opposite is true in that they have better NV than you.
You aren't penalised for not doing missions beyond the loss of potential score and rewards you could have got by going - so for pogroms, for instance, you can skip entirely until later in the game if you want.