I play with a Minas Tirith army most of the time, and what I basically do is create a frontline of Minas Tirith Warriors with shields, then add Citadel guards + spear and Rangers with spear to support this line. This way you have a line of F4/D6 warriors, which is IMO more effective than having Defense 6 spear support at the cost of Fight 4.
I
always add 3 or 4 knights, they are very effective at killing single warriors without support (I find charging more than 1 enemy with 1 knight to be a bad decision most of the time, unless you're facing Fight 2 goblins
.)
GotFC with shields are also great (use them against Strength 4 heroes etc), although I don't field more than 3 most of the time.
As for heroes, Beregond and Damrod are a must have in almost every army because they are cheap and able to lead troops. I'm not a fan of using Denethor though, unless you are already using both Beregond and Damrod.
I also prefer Madril over Cirion, because he has a bow and his reinforcements rule is extremely useful in some scenario's!
Now that Faramir can have a shield he's become waaay more useful. If you mount him on a horse with a lance he can be very effective at killing units, while his D7 gives him some extra protection, which means he could be chosen as your armyleader
Unfortunately Boromir Captain of the White Tower is never worth it's points IMO, I wouldn't even field him in a 700p army list. Boromir of Gondor is very good though! His 'weakness' of not being able to field troops can be negated by using Beregond and Damrod. He's better at 500 points than 700 points because you'll see less wizards.