Make as my settlers as possible.
I cannot stress this enough, because I know people that will only make 5-10 settlers a game. Next game, try to get at least 10 settlers on each resource, and observe your muchly increased production. I find a good amount of settler to have is 80 (30 farming, 30 plantationing and 20 chopping.)

If it suits you, raid.
Every once in a while, make 5 or so hussars and send them to your opponents base. Avoid defensive buildings and troops, just kill their settlers. When their military comes after you, run away.

Be ready for raids and attacks.
Often times you will chop out all your trees and send your settlers into more exposed territory. Either bring with them some troops (around 10 should hold the enemy off long enough for your settlers to escape), or build an outpost. Your settlers can garrison in the outpost and survive long enough for your defensive troops to come to their aid. Keep around 20 units in your base in case your enemy decides to attack you, which they should often do.

Dance.
I don't mean get up and shake it. It's kind of hard to explain, so I'll give an example. So your 10 mercanary cav archers are against your enemy's 10 skirmishers. You will win the battle, but take losses to your inreplaceable mercanary forces. Instead, when all the skirmishers fire at one of your archers and it get heavily damaged, reatreat it, and let them fire upon another one. When they do so, retreat it also. You should also rotate your damaged troops back in. This way, your guys will be damaged but you should take no losses. Just use your priests to heal 'em.

Be respectful.
Some people have th theory that if they use proper grammar everyone will think that they are a brilliant military tactiction and will not want to play you. It is just the opposite. If you say things along the lines of "OMGLOL i will hand u ur bum in a dysplay of onwage and u r teeh GAY!!!!!!!!!!!!!!!!!!", you are degrading yourself.

Help your allies.
If your ally is attacked, help them unless they say not to. Oftentimes I will attack a player and beat him and/or her easily, and when I move on to him teamate's base it is crawling with "l33t units".

Hope this helped.