I usually play someone squishy - like a Sorc - so I like using the far right formation where the Charname is in the center, and I can surround him with the other NPC's. If I'm playing melee, I usually stick to the two-row formation as I don't mind leading with my main char.
Depending on my class, I will either use one of the two triangle formations with Charname at the front (if fighter) or back (if bard, thief, etc.). My favourite is the pentagon one with Charname at the centre, though. I like the way it looks.
Spread out triangle for wilderness exploration, zigzag line for dungeon crawling. I put my thief in e third spot and check meticulously for traps. The zigzag is concise and the only formation that I can fit down halls without the characters being slightly out of formation.
In the unenhanced BG, your party did not "bump" into place if there wasn't room for the formation or someone needed to walk through someone else.
I pretty much go with the pentagon out of habit because it was the easiest to squeeze into hallways in those days, in my opinion. It didn't have the follow-the-leader formation, either.
I use the one that is like default column formation, except with one of the columns slightly further forward than the other (and the columns a little closer together than in the default formation). I think it might be the zigzag one mentioned above. I like it for being compact, as well as having one character slightly more forward than the other. This is in part so that you're better able to focus enemy fire on your tank at the front, as well as to try and make sure that your party leader (that hopefully has high charisma) is the one that does the talking when someone initiates dialogue.
I prefer the 3 x 2 one. 2 x 3 when indoors with lots of corridors. I did use the pyramid formation for a short time on advice of someone here on the forums to help with map exploration, but ever since Neera learned Clairvoyance I just have her cast that through Nahal's Reckless Dweomer... granted that often takes several attempts.
2 x 3, the basic formation. 2 fighters in the front line, healer and rogue in the second line, wizard and whoever else is on the team come into the rear line. If there are three melee warriors, the rogue is put at the rear. This formation brought me victoriously through the Sword Coast, the Lands of Intrigue, and the Spine of the World (and the other regions you make a visit to in the games). .
tank and healer at the front, other and rogue in the middle, mage and tank at the back also formatted so that when i spin the formation the tanks and other (usually special DPS: blade, kensai, archer etc) make a front line of 3 with the mage, healer and rogue in the back line
Comments
T-formation for dungeons and more enclosed spaces. Meatshields in front, squishy casters in back.
Default column formation for very small rooms and spaces in dungeons like Durlag's Tower.
Indoors: Column is the only thing that works
I pretty much go with the pentagon out of habit because it was the easiest to squeeze into hallways in those days, in my opinion. It didn't have the follow-the-leader formation, either.
x x
x x
x
Edit: lol nwn! The hexagon-like one.
Yep, that is the zigzag I was mentioning. It works very well, but outdoors I switch it up because I have some more room.
@dib
Good idea to uses those x's
X..
..X
X..
..X
X..
..X
This one is my favorite, .. Means blank space
tank and healer at the front, other and rogue in the middle, mage and tank at the back also formatted so that when i spin the formation the tanks and other (usually special DPS: blade, kensai, archer etc) make a front line of 3 with the mage, healer and rogue in the back line
..x
x..
..x
X..
..x
x..
instead of
..X
x..
..x
x..
..x
x..
The former is preferable when the party leader is not a tank.