Quote Originally Posted by Invicta
Do you group your units on unit type or left-flank / centre / right-flank?
Grouping is important especially so in mixed RTW armies.

The new speed and kill rates in RTW require players to initially form a long, but solid line (only on defense; on offense, you can separate the cavalry a bit on the wing with some infantry backup), therefore you can't have gaps or the heavy cavalry will own you.

The center must be strong because:
1) This is the best place to house and protect the archers.
2) If the the center breaks, helping out from the flanks will have you sandwiched by the AI's own flank. This is not true if one of your flank breaks. You can compensate with the other flank plus the center.

Thus, the General must also be behind the archers,
1) To reinforce the center.
2) To give your center troops extra morale boost.
3) To reinforce either flank.
4) To rally routers.

In STW/MTW, you can have gaps in your line because:

1) You can separate your archer units to the flank.
2) The slow speed enables you to react fast enough to counter the AI.
3) The slow kill-rate enables separate formations to help and flank.

These are very difficult to pull off in RTW.

With flanks/center grouping you can visualize the location of your troops and click on the unit card.

1) making your reaction faster.
2) minimize the need to pause.

ex: If you are in the right flank, how do you move to your left flank?

ans: click on any of the unit cards of the left flank group.

If you use a fairly homogeneous army then, grouping is not as important.