Defensive English Longbow deployment:

.BmCvIT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .BmCvIT.
. . . . . .LbS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .LbS.
. . . . . . . . .LbS. . . . . . . . . . . . . . . . . . . . . . . . .LbS.
. . . . . . . . . . . .LbS. . . . . . . . . . . . . . . . . . .LbS.
. . . . . . . . . . . . . . .LbS. . . . . . . . . . . . .LbS.
. . . . . . . . . . . . . . . . . .DsK.DsK.DsK.DsK.

BmCvIT = Billmen in Woods/Cavalry in Open, or Impassable Terrain.
LbS = Longbows behind Stakes.
DsK = Dismounted Knights.

One tactic that works well in M2TW is 'enfilading' or flanking fire. Essentially all missile troops do much more damage to the enemy by firing along their line than by firing from directly infront of them. This is especially true when firing into an enemy's unshielded side.

By sweeping the Longbows forward into a shallow V-shape, enemies advancing against you are exposed to lots of flanking crossfire regardless of whether they target your centre or wings. (With some exceptions playing on Huge Unit Scales, where the Longbows lack the range to cover each other completely.)

However for this formation to work ideally both your flanks must be anchored. Farmhouses, City Walls, Rivers or Cliffs can be used to this effect for a strong anchor. Failing that, rough terrain troops such as Billmen can provide a similar effect inside woods. Failing that Cavalry can be used to defend the flank as best they can in good going.

Failing that, you must rely on the M2TW AI to ignore your flanks and charge your centre. (Which it may do.)