Gonna pimp the intro thread, as some of your questions are answered in there:
http://www.dakkadakka.com/dakkaforum/posts/list/474150.page
Seamus: Uses his undead hookers to lure your enemies' models away from his edge of the board, and towards you guys. You lure them in, and then Seamus tends to go in for the kill. Lots of lures can really mess up your opponent's game by pulling things out of position, using it to bring things out of
LoS, etc...
Viktorias: The sisters are both decent in combat (though one is slightly better than the other). They like to buff each other, as well as use Sisters in Spirit and switch places with each other, or bring the other one closer to her. They also like having Ronins in their forces so that if 1 viktoria dies, you can always turn a Ronin into a new viktoria.
Perdita: She is the anti-neverborn master for the guild. Her and her family are good at shooting, and good at putting down the neverborn. She's quick and likes to be around several of her family members as they can all activate at once, giving you a bit of an advantage as you get around the you go I go activation system.
Hamelin: Kinda broken though I've never seen him played as such, but he uses blight counters to slowly kill your opponents off. Careful as there are 2 versions of Hamelin, the minion (Hamelin, Ratcatcher) and the master (Hamelin, the Plagued). They are the same guy, and cannot be on the board at the same time (i.e. you can't take both of them in your crew). Think of his minion form and his master form like a regular caster and an epic caster in
WM (though minions can't lead crews)
Somer: He has two very distinct ways to play. 1 is the gremlin gunline, where you just get a bunch of Bayou gremlins and go to towns. You can heal them and blow them up if you need to as well as using his Git Yer Bro to summon more gremlins.
The other way you can play him is using tons of pigs, piglets, pigapaults, etc... It all depends on what you want to do, just remember if you take his totem, take 2 of them.
The dreamer has one basic strategy which is the Nightmare Bomb. This involves starting the dreamer on the board with nothing else deployed on the board. Then you use his flight ability to move 14 or more inches across the board (he has three general
AP to use a turn as well as instinctual which grants a second (0) action). Then you either let him die or you harass your opponent. When the Dreamer dies, ALL buried nightmares come into play. This means LCB and any other nightmare in your list pop up within 6 inches of where he died. So you could theoretically have a 1 melee attack if your opponent kills the Dreamer fast (he only has Df 2 and 3 wounds).
Hope that helps