I play very bad. Really, really really VERY bad.
Especially very slow.
Using "normal" game (defend a little, boom a little, attack a little, depending on how well you are), I do not win all games vs. Moderate AI and tough AI kicks my butt more often than not.
Now behold I can kick any difficulty AI without any trouble (even TWO AI at that!).
All I do is repeat and repeat the same process that Out4Blood and others taught us: Do the Ol' Ancient Rush!!!
I have already taken 2 Toughest AI with it - and 1 is more often than not won by me.
But it really becomes VERY boring.
Now my opinion is that anybody that is not very, very fast player has no chance vs. toughest trying to boom and attack the "normal" way.
You must raid very early and also attack very early. Also, when you rush, due to the fact that the AI quickly puts up a big defense (it has many more resources than you and has cavalry sooner), you need to adopt a military-oriented development and assemble a reasonably big army to take down their Capital.
If you go "150", then take a big party. If you go simple "delayed", it is a great idea to take also 2-3 archers and put them in raiding mode all over his place while you and the AI are busy around their Capital.
Basically, the AI's economy MUSt be dismantled very quickly, so that you can boom + raid the whole game.
Of course this is me, a very bad and slow player.
If it works for me, then it must work even better for you faster guys.