Lets start with the basic strategies: rush, boom, and fast fortress. If you rush against a capable boomer you will lose. If you boom against a fast fortress you will lose. If you fast fortress against a rush you will lose. This is assuming that the players are of equal skill.
Rushing is designed to disrupt economy and win the game without ever getting to age 3 (that is the goal, but not always the case). Sometimes rushes fail and are forced to age three or the rusher is not as committed and goes to age 3. Booming is effective because you have a smaller army designed to counter the rush on defense and most of your resources and home city shipments are economic base so ultimately you can age 3 faster than the rusher and dominate him with your superior units.
A fast fortress is effective against the boom because your age 3 units (or mercs) can destroy defenses and kill villagers very effectively. You sacrifice economy and rush defense for stronger units. I am developing a dutch fast fortress where I can get mercs in ten minutes. Still ironing out the the chinks and flaws, but a detailed post is forthcoming. The fast fortress is beaten by the rush because you generally don't have the defensive ability of boomers. Rushers disrupt your economy and if you get age 3 you won't have the resources to field an effective army against the rusher.
Some Rush Basics:
Here are some basics so you can rush with any civ. Obviously not all civs are meant to rush, but this will give you the ability too.
All you villagers on food untill you can age up. With Dutch you want 4-5 on gold, but the rest on food. How many villagers you actually build depends. Ottomans normally have 8 villagers before they age up. Spanish advance with a low number as well. Russians can go up with 14 and french around 12. British can do 15 or so since they get vills from houses. Germans can get 10-14 with settler wagons. Portuguese can go 12-14. It depends on your strategy, how fast you want to advance, and the units you want to build once colonial. I may be wrong on total counts and there are obviously variations, but the basics again.
All civs normally have time for one card in discovery. You have to decide what it is. I like the 300 food, means you can age up faster. Furior helps a ton, and settler cards have their advantages as well. Call is yours, expirement, see what works best.
You first age 2 card should be military. For ottomans it should be the 5 jannie card. For alot of the civs the 3 hussars (or 5 uhlans or 5 cossacks). That way you can raid fast and possibly kill his forward villager. Other options are pikemen or crossbowmen. I have seen an effective pikemen rush with the spanish where they age up fast and go right for my houses, it sucked. Of course back then I was still doing a 17 settler rush as russians so I don't know how effective it would be against me now.
Keep building your economy and your army. Focus on his settlers, but keep your units alive. Don't fight a battle under tc fire or tower fighter unless you have clear advantage. Attack and retreat, attack and retreat. Keep him guessing and keep massing an army big enough to whipe him out. At one point you may have to back off and age up, but keep the pressure on with small raids. This is the basics.
Basics of booming:
The idea is that you trade military strength for superior economy and then you overrun your enemy with a larger army that you can mass due to your bigger economy. Getting market upgrades and constant villager flow is critical.
At the same time you need some defense, so work for counters. Cav rush, pikemen. Infantry rush, crossbows. Abus guns/grenidiers, cav units. Some may disagree, but I think raiding while you boom is critical to keep his economy steadily weaker. Build towers next to your resource gathers. The idea isn't for your towers to kill units, but rather let you hide your villagers till his army moves on you counter it. Get a big economy focusing on wood and food first, then move to gold and age up. Once up you have an amazing economy and can just run over your opponent with superior age 3 units.
Basics of a fast fortress:
I have little knowledge in this catergory, but I have had limited success with going for a rush age up. Once up build a handful of villagers and focus on food and gold. Use homecity shipments to boost your resources can go up asap. Once up get mercs, the 2 falconents card, or anything else that strikes your fancy. At one point you will want the extra tc card to help improve your weak economy.
I saw an interesting recorded game where an ottoman did a fast fortress. Obviously the opponent suspecting rush and built as such. The ottoman aged up fast and overran him with mercs. It was kind of cool.
A few reminders:
Raid. I think except maybe in the case of the fast fortress you need to raid in regardless of the strategy. Raiding disrupts economy and forces opponents to build counters that may or may not be effective against your main army.
Get trading posts. Not to early, it is a waste of wood, but sometime getting trading posts mean faster homecity shipments and an edge.
Get injuns. Native Americans provide an edge in techonology and some cheap units that don't cost gold.
Scout. Nothing is as critical as good scouting. And continuely scout, be aware of where your enemy expands his economy and builds. This edge means you can effectively raid and dodge fortifications.
Accept all challenges. It is a chance for you to be better. Nothing pisses me off more than when someone is scared off by my high homecity level. This is more a personal thing me telling noobies to accept all challenges so i can beat up on them, but seriously it will improve you game. In AOKH I had an Operation Ladder Champ thing where I spent about a month playing the best players I could find. I lost alot, but then I played my boys and people formerly at my level I dominated.
These are some observations and I may be wrong on some of these accounts. Please, correct me (preferably in a polite manner, but you can be an asshole if you want). Strike up some hearty debate if you want as well. I like you guys, we should be friends.
-Benjamin Franklin