The End Of Peace
It looks tempting to recruit lots of Wolf Riders to match the humans' cavalry mobility, but don't try -- they're not quite a match for cavalry and tend to get cut to pieces in detail. Two Wolf Riders for village stealing is enough, recruit mostly Orcish Grunts and Orcish Archers instead. Keep close order, pot the cavalry with archers, and bodyguard the archers with the grunts. Kapou'e can do a second round of recruiting at the neutral keep near the east edge of the board,
The Human Army
Avoid this scenario; it is basically impossible to beat. You'll be given the option at the end of the first scenario.
Towards Mountains of Haag
Keep Kapou'e and your troops moving and try to brush the dwarves off your flank as you pass, because if they get to mass on you and fight a static battle they will chop you to dogmeat. Recruit at most for two rounds and run for the signpost at least until the trolls show up. Then, if the odds are with you, you can linger a bit and harvest some EP. Again, your archers are your best offensive tool (since the dwarves have no missile attack) but you need to use Grunts and Wolf Riders keep the dwarves off them.
The Siege of Barag-Gor
The key to winning this one is that, even though you get a nice allied troop surge in Barag-Gor at the beginning of turn 2, you shouldn't waste your own troops in a futile effort to hold the city. Instead, run the trapped shamans out as soon as possible; a gap is likely to open up to the SE around turn 3. Take your troops south to knock out the elves there, then west, then north. Don't forget to liberate the caged assassin at the western keep.
Towards Harbor of Tirigaz
The northeastern enemy can be blocked with a couple of veteran units at the river fort; do that while you take villages on the near side of the river with your shamans and take a recruiting round or two of troops south to deal with the southwestern enemy. Ignore the holy water as any unit that reaches it will just drink it.
If you run Guu and Kapou'e straight south to the central keep (not stopping to grab villages unless you can end a longest possible move south on one) you'll get to recruit trioops in time to meet the first pirates on the beach. This will be good as fighting from the water hinders them. Punch out Harmon's (southern) keep first, then roll north.
The Desert of Death
Pick troops with lots of mobility because the desert is hard to move in. Use your shamans' ranged attacks against the giant scorpions. Head southeast towards the near edge of the big lake; the enemy you'll need to defeat is there. His troops aren't very effective but beware of letting isolated units get swarmed.
The main thing to know here is that the elves have a 100-per-turn income; you can contain them long enough to get Inarix to the river but you can't beat them. Block the elves with a strong force (they recruit L1s, so this is a leveling-up opportunity), bloody the dwarves with a slightly waker one, and run Inarix up the middle.
Clash of Armies
You have no healers, so this is a test of how efficiently you can cycle units from the fortifications back to villages without losing them. Your left flank is more exposed than your right as there will be gryphons and the occasional merman (they become rare after the first surge). Hold the river bastion or bridge if possible; if they get to the shore hey'll be able to widen the front and make better use of their numbers. Orcish Slurbows will be really useful.
A Dwarvish Stand
Recruit Wolf Riders and other types with lots of mobility, because just mushing through the snow to get to the enemy units is work. Let your allies get in front of you and screen your troops; you might even conaider no recruiting for two turns to let then get ahead,
This is a big, messy brawl. Your allies will show up late but in large numbers. Concentrate on the human and elvish keeps nearest you, allies (including Gruu, who you'll play when he arrives) should do an effective job of squashing the others.
It's difficult to get this one finished in time unless you divide your forces and get maximum use from the roads. Send two groups at the northwestern and southeastern keeps, then converge on the southwestern one.
Lots of scenery -- and lots of villages -- in this one. Build two or three wolf riders just to run around grabbing villages, it will pay off. The AI will tend to move his units north to grab the coastal villages; encourage this by sending a handful of veterans in that direction to draw more troops north even as you run your main body down the road towards the city gate.
Let your ally-generals soak up the casualties; use them to screen your flanks and your movements. A static defense on the city wall will work, or you can recruit a large army early on and punch down the middle; that has the advantage that you may be able to take out Earl Lanbec'h before a lot of his reinforcements arrive (they show up at the south-center edge of the board every morning).
Your first job is to bust Kapou'e out of the ring of grey orcs, then run Kapou'e north to the main keep where he can recruit. Your ally generals and Howgarth cannot just quite neutralize Earl Lanbec'h, so split your troops and send half south and half east after Shan Taum.