Tips on battles with Factions (Medieval)

I usually find thatif I use the same strategy with two different factions with two different units (i.e. Romans and Greeks), I get slaughtered. This only just when I get too tired to remember who I am playing as; Brutii or Greeks.
The purpose of this topic is for all the serious strategists and tacticians to help out all those who struggle by posting their methods (or as much as they would like to) to help those less able and have resorted to auto calculated battles (almost no point when the game is about the actual battles [empire builing yes, but more for the battles])

In the intrest of keeping it easy to find which Faction in which Game (Rome, Medieval, Shogun), I am going to try open three different posts unless of course the moderators decide to link them up. Please Don't I am just trying to make searching easy for people.

This is for Medieval tips

Medieval 2?

EDIT: Of course your refering to M2TW.

I think this is for plain old medieval....

yeh i believ it is for the original medieval total war.....i have to wait a month and 6 days till i get M2TW...........it is absolute AGONY

In Medieval (as with anything) tactics depend on many variables. Any battles in specific?