Hi there, I translate one of my fellow's problem here.
He is a MT player. We are going to make a 400 points battle. No Warbands rule, but you must bring one named hero and a captain.

Could you please give me some advice for an effective MT army list against an average Urukhai army, morannon orcs or Black guards?

The problem is these evil guys are frakin strong, and cheap.

How should I defeat them? I'm going to lots of MT warriors, but I won't use any ally.

Which type of archers should I bring? Rangers or MT archer?

Well if your not playing by updated rules, then your army is going to suffer some of the problems your facing. Under the updates, Gondor can actually spam just as many troops as mordor because of Damrod and Beregond. I would have said you could match thier numbers pretty well but not anymore.

In this case, you should stick to a fight that your opponents can barely win, which is to have a phalanxe with Fountain court Guard in the front, Ithelien rangers with bows and spears in the middle and Men at Arms with Pikes in the back. I would say use Halbarad as a banner but im not sure if you refuse to ally with him in Arnor (technically it is still Kingdoms of Men so it is the same book). If not, just pick a couple banners.

Essentially you will outfight him with 3 dice (one re-rollable), and you have archers in the middle to make him come to you. Fountain Court guard can better handle the strikes from being trapped since if you give them a shield, an opponent still needs 6's. I would say throw Malbeth in the mix, but at 400 points, that might be hard.

Still I think a Phalanx is the best way to deal with an overwhelming horde. Just remember to guard your flanks.

400 points isn't a lot of leeway, so be sure your named hero is either Beregond or Damrod. I'd prefer Beregond for his better bow and higher armour. If you're not taking allies, you can't take Men-at-Arms with pikes since they belong to Fiefdoms. This means you're going to need as many spears, higher fight, and shooting as you can pack into one profile, which spells "ranger"

WoMT in the front, rangers with spears in the back. Fountain guard with shields are very effective, but I would keep them behind some WoMT: their spears still lend F4 to the fight, but if the WoMT fall you still have F4 and a tough center. If you lose your FG first, then you no longer have F4 and your center is soft.

Yeah I forgot that you meant you dont want to go out of the Minas Tirith section of the book. I guess Men at arms are out. Pretty much everything Whafrog said is the best advice.

EDIT: Actually I have to disagree on one point. I would put the Fountain Court Guard in the front. The reason is because you are likely to face Morannon which will butcher WOMT. They will only need 5's to wound, but 6's against a FCG with shields. This will help limit your initial casualties and give you an edge in the late game.