Hammer is all about damage... and knockdown. Seeing that you will probably use less tactics skill in this build, you might want more points in Strength for the Armor Penetration instead. Hammer uses quite a lot of adrenaline... so I tend to stay away from "Lose all Adrenaline" skills.

Skills:
Hammer
Crushing Blow
Might Blow
(Irresistable Blow)
Staggering Blow
Counter Blow

Strength
Endure Pain

Healing Prayer
Healing prayer/Healing Signet (tactic)
Mending
(Balthazar's Spirit)

Basically, chain up the different blows once you have the adrenaline. When you chain things up, you will basically knockdown, apply deep wound, weakness, huge damage, and kill. You might want Balthazar's Spirit for the adrenaline and energy, or you might want Irresistable Blow for the unblockable factor.

When you go with a party, ditch Healing Prayer and take a Resurrect skill instead, and because of that, ditch Balthazar's Spirit since you won't need Energy anymore. Take Sprint to chase down caster/ranged foes instead.

Hammer's max is at 18-35 IIRC... not sure about the 18. With a high strength, you should be able to do good damage to any type of enemy. You will want to go for the highest defense for armor + reduced damage (Ascalon/Knight amor) because you don't have the extra defense from shield.