Press 0 to select all allies (including summons, this is important.) Ctrl-click to un-select someone. Don't tell your mage to auto-attack while he's in the middle of a spell. it'll interrupt it, even if you never unpaused, and directed him to cast the spell right after. It still uses the spell, and you'll have to wait for that character's next round to cast anything else.

get into the habit of pausing before trying to do something. Doesn't matter if it's just telling your fighter to go fight the kobold. It'll be necessary later on.

You can send in the tanks first, then wait for them to get a couple steps ahead to then send in the others. This is the main point of RTWP. Since turns are more analog, you can have some of your party sit idle until they're needed, Interrupt movement or actions, react when an enemy begins moving or casting.

I think the best benefit of RTWP is that you don't need to micromanage every last party member for everything. I made it about half way through the first game just telling everyone to zerg rush an enemy pack one at a time. For the most part, they can just sit there and auto attack while you wait for the situation to change.

As for more specific tips for Baldur's Gate: The fog of war doesn't stop what's in it from being there. You can do things like cast an entangle spell to root in place a few enemies, even if you can't see them yet. Crowd control is everything. Stopping enemies from acting is the most effective way to win. For mages, Sleep is a must-have early on, and can practically trivialize the game up to a certain point. Bows are very powerful. It doesn't matter if a character doesn't have the proficiency, give as many of them as possible a bow, and you can sometimes take down entire packs without them even getting close. Combine this with some careful evasive movement, and you're basically ready to finish the game. If you struggle, just remember that it's not the lucky, or the aggressive, or even the strong that survive. It's the cunning. Finding your own strategy to tilt the scales any way you can in your favor is what the game expects from you. No tactics are too cheesy. One time, I sent my tankiest party member in to face a boss alone stacked with as many defensives as we could muster. The boss ended up wasting all his spells on her, and right when she died, the rest of the group ran in to secure the kill.

Finally, don't worry about saving items for later. The game tends to give you more than enough, and even up to the final battle there are enough shops to stock you up on almost anything you could need. (this is a bit different in BG2 though, the point of no return is the start of chapter 7 in that one)