It often happens that your party is approaching an area in which you just know combat will soon ensue. Or, when a combat encounter presents itself, you may be given an opportunity to arbitrarily choose the placement of the PCs within a certain section of the battlefield. In these scenarios, it's typical to establish a standard "marching order" or "formation" in which your party will approach.
For some character roles, it's very clear where they need to be - Defenders up front, Controllers in the rear, and such. But, for some others (and depending on actual party size and makeup) things get a little fuzzier.
I'd like to establish here a CW of general, tactically optimized formations for parties of 3-6 characters in various scenarios. Especially noteworthy would be hallways ranging in width from 1-3 squares, but wide open spaces and other special configurations would be nice to have as well.
Of course, some characters' optimal positions will depend on the actual build of the character. But I believe a large percentage of parties may still benefit from some generalized formations which could be used as templates from which to design their own strategies.
I suggest using the "code sample" formatting, to get a fixed-width font representation, using the following symbols
D - Defender L - Leader S - Striker C - Controller x - Difficult Terrain X - Blocking Terrain
As an example, here's one scenario I'm currently looking at: Two Defenders, one Striker, and one Controller, in a three-square wide hallway. One formation I'm considering is this:
XD DX X S X X C X