Strategy (A)Strategy (A) tends to involve: 26 or 27 vil feudal, wheelbarrow in Feudal age, 3-4 gold miners, plenty of farms. Your Feudal Age buildings could be stables+blacksmith. You should probably create one scout in Feudal, so that your knights can see where they are going. Ideally you want the first stables on the enemy side of your town, and a second stables as far forward as you dare. You might partially wall in your town, or the most vulnerable part, with houses + barracks + blacksmith + stables; do not build stone walls or gates. In early Castle, build a second TC as soon as possible: without mining stone or building a market, this is the most you can do as you only have 100 stone at this stage. Personally I build the second TC six tiles away from the first, for mutual protection and so that I can create a vast farming area; I ignore stone at this stage although gold is worth going for.
Create knights from both stables, if necessary at the cost of a small delay in villie production at your TC(s). Gatherpoint the knights as far forward as you dare. When you have 4 knights, hit the enemy. Alternatively you can hit the enemy earlier with 2 knights, and send another 2 knights to another part of his town 30 seconds later on. Even if you lose the first 2 knights, it is probably a worthwhile exercise if you can kill 1-2 vils and/or make him garrison his vils for a significant length of time. Fairly quickly you should be able to maintain continuous villie and knight production from 2 TCs and 2 stables respectively, then you can start stone mining, build the 3rd TC, research stuff and boom away. I used to make the mistake of researching blacksmith upgrades before building knights, but I now realise that is generally not the best use of resources until you have 10 knights already built: it's better to have 4 knights than 2 upgraded knights, etc.
Exceptionally, if you have superfluous food during the Castle transition and plenty of sustainable food income then you can research Blacksmith upgrades. I would research the attack upgrade before the armour upgrade because it will enable you to kill a vil in 4 hits instead of 5 (I think that's right, anyhow you get the idea).
IMO, Franks, Mongols, Persians, Spanish and Vikings in particular should usually go for strategy (A). For various reasons, these civs are able to create more knights, sooner, than other civs and they should press this advantage home. (Vikings not as good as the others, and they don't get Bloodlines, but it is still Vikings' best strategic option as Vikings are at their relative strongest in early Castle.)
Saracens and Turks can do it too. Equally, they can go for the same quantity of camels to counter an enemy doing this strat, or to help out an ally. As an alternative, Turks can do an earlier light cavalry raid (maybe buying food at the market).
Chinese players almost always go for strategy (A), which is, perhaps, a reason why they should not as although the Chinese can strike with knights while the enemy is still in Feudal, the enemy will almost always have built heaps of spears. On the other hand, the Chinese could be cunning and hide a couple of forward barracks near an enemy who is further away, who might not have had the foresight to build spears. The possibilities are endless.
Meso civs often go for strategy (A), although personally I don't like it as a small handful of EWs is a fairly weak force; although if you can build 15 EWs from 3 forward barracks by 25 minutes that would be a different matter. If you don't forward build, one problem is that on an 8 player map (typical for LN) the EWs simply don't run across the map fast enough to attack at the earliest, most devastating, time.
Strategy (B)
Assuming you can defend reasonably well against small scale raids coming from enemies implementing Strategy (A), Strategy (B) can turn the course of a game. The idea is to boom from 3 or 4 TCs, with a view to building a later, but stronger, Castle Age army. This army should be sufficiently powerful that if you raid with it, it can knock out an entire enemy TC and remain relatively undamaged (unless the enemy matches with an equal sized army). Alternatively, if your ally is engaged in a 1v1 or a 1v2, this army will turn the course of the battle and ensure that your side wins. I would say 20 knights, with some support (eskirms, camels etc) would be a minimum size army under this strategy.You can build up this army near your base or at a point between you and the nearest enemy, so that it can serve the function of defending you against raids in the meanwhile.
You obviously need to mine stone (or buy it in the market, which is very inefficient unless Saracens but it is probably sensible to do it for the first 100 stone needed for the third TC). Your third or fourth TC will probably be on stone. Because you will be building up your army later, you need to be able to do it faster so you should start with one stable (keep wood for booming), and add three more stables when you can.
You could do a 25+2 vil, blacksmith+market fast castle, then wheelbarrow from the second TC as soon as it is built; ideally you need to have the resources to build both the second and third TC as soon as you Castle although this can be difficult with this size of economy. You will probably get all the Feudal economic upgrades, and the Castle wood upgrade, but don't bother yet with Heavy Plow because it is costly to research and its bonus doesn't save you any resources until at least 30 minutes (i.e., the time when your farms built post-Heavy Plow would be still going, had you researched Heavy Plow at 25 minutes, instead of expiring as they will do if you don't research it). By that time, wood should be plentiful and your army should be on its way to do its damage in any case.
Strategy (B) is good for late castlers, i.e. Huns, or for people who had a bad start for one reason or another (e.g. no sheep and no hunting). Huns, in particular, are at their strongest doing this strategy, because it involves a rapid build-up to a pop of 100 or more by 30 minutes, and every other civ would have trouble keeping up with the housing for that whereas the Huns civ bonus really comes into its own doing this.Strategy (B) also encompasses non-knight armies, i.e. massed crossbows or massed cavalry archers, in both cases with pike or camel support. Thus it is a good strategy for Britons (excellent early boom, excellent crossbows); Mayans (early Castle leading to excellent boom, cheap crossbows); Huns (cheap cavalry archers); Saracens (good cavalry archers, wood+gold based economy). Apart from Saracens, these civs also have difficulty in doing strategy (A).It is also an option for Chinese, as it is slightly unexpected for them, and it makes excellent use of the early Castle time and the cheap technologies.
It is essential to have a few spears or pikes at home, and a reasonably well walled-in town, in case any enemy knights slip through the net.
You should research Cartography if doing Option (B), as you may well need to send your army to help out an ally who is being doubled.
Strategy (C)
A pure boom (a boom + 8 pikes at home, or a boom + 4 camels, or a 2 knight raid in early Castle + boom, all count as a "pure" boom for these purposes) should only be attempted if you have notified your allies well in advance and they don't object. You also need to be in a pocket otherwise you will get raided so much that it fails.Even at a good level of play, a boom is respectable if (but only if):
(a) you know how to defend against a raid (pikes);
(b) you boom well, and you know how to fast imp and do something useful and game turning when you do (champs or siege or UUs or a really massive army);
(c) you have a civilisation which is at its strongest in Imperial (Turks, Teutons, Koreans, Byzantines, Goths, Aztecs, Celts);
(d) you are willing to tribute resources to your allies who are not booming (see 'Slingshot' below)
Ideally, no more then one civ on a four person team should boom. Essentially, three keep the enemy busy, while one booms and then comes along in Imperial to strike the death blow to the enemy. You should be strong enough to attack two enemies simultaneously, as one of your allies may be in retreat at this stage in the game due to lack of help from you.
You probably need to partially or completely palisade wall your town/corner of the map (single layers of walls - you are just trying to keep out pesky raids), and you certainly need to maintain spears at home - you may maintain 12 spears instead of 8 pikes, to save on the pike upgrade cost at this stage.
In practice, it is possible to achieve something like a 34 minute or 35 minute Imperial time on LN, but I think 36+ minutes with a stronger economy is better. You are probably looking at something like 5 or 6 TCs, but few military buildings until you start the Imperial upgrade.
Most rooks play this way. The difference between a good player and a rook in Strategy (C) is: the good player can boom from 3-4 TCs as soon as they hit Castle age; the good player will only do it where the conditions highlighted above are met; the good player will only do it where his allies agree; the good player will hit Imperial by 36 minutes and have a powerful army ready to deploy as soon as he does hit Imperial.
Champs are probably the best option for most civs under Strategy (C), as they are the easiest to mass, and yet they defeat virtually any Castle-age unit 1v1 and they rape and pillage enemy towns.In my view, Teutons are particularly suited to strategy (C), with a slow castle time but a good boom due to the cheap farms, fully upgraded champs, powerful siege, a great UU, and very effective base defence due to the TC attacking bonus. Teutons should be able to fast Imperial and tribute several hundred food to their allies if need be.