Rules Of War

1. Know you enemy
2. Know yourself
3. Win a battle without fighting it (in Mordheim's case make sure none of your units are OTT). If you can accomplish that then you are truly a great general\war band leader.
4. Prepare for the worst
5. Plan well how your war band is equipped
6. Give each or groups of units a specific role
7. Assumption is the mother of all *&%$up's
8. If they hit you hard hit them harder
9. Never be Complacent!
Always remember that all other war bands are formidable opponents & are all well rounded groups. 
Dwarf Disadvantages:
Dwarfs suffer from one major disadvantage, they have a normal movement of 3" and 6" for charge. Their tiny legs can't keep up with he rest of the warhammer races. However there toughness of 4 and Hard to kill rule ( hard to kill : can only be taken out of action on a roll of a 6) makes up for this extreme disadvantage. Also Dwarfs are not known to climb building with ropes or ladders, with an initiative of 2 no one blames them. However to combat this make sure these sturdy dwarfs have ropes. And implement a rule on ladders which can be bought in the Traders section... but put heavy restrictions such as : The dwarfs cannot do anything this turn but climb the ladder. Unlike Elves or Skaven (Elves with a natural initiative of 6. Skaven 5), They cannot Wisk themselves up a building with ease.

Turning a disadvantage into an advantage: 
The Small movement dwarfs have makes the game for the dwarf player and calculated and very strategic battle, because of the small movement, were you put/position yourself is vital. For instance most scenarios are dependant of the war band holding or capturing even moving to the other side of the table, and with a 6" movement that's takes a long time. Elves move 20" max in two turns while dwarfs move 12". To counter you have the access to fire power with extreme long range if you include an Engineer in the war band (Engineer is vital). Dwarf Crossbow and handguns get a range of 36" (crossbows) 30" (handguns), which if you play on a 4by4 board covers 80-90% of the battlefield. 
The key is to position your missile troops in key areas where the get a wide range of fire, so that enemy thinks twice before moving his\her units into a key position. At least start with 3 missile troops if not more. Use your long range to shoot down the enemy unit ( shooting enemy missile unit would be even better) before they can reach there objective. Unfortunately the dwarf henchmen have a BS of 3 compared to Elves and Henchmen BS of 4. To counter this make sure you have more than 3 missile units to begin with . Pistols are a good weapon to with a range of 12" due to the Engineer it's a bonus. 

Dwarfs Toughness and racial skills

This is what counters the dwarf poor movement and initiative. There toughness is a bonus which the dwarfs are heavily dependant on. It makes them harder to wound and makes your opponents frustrated that there arrows and sling missiles keep bouncing of the Dwarf unit. Plus there toughness rivals even the strength of the cross bow and hand gun, usually against the majority of units in mordheim (Not including dwarfs) Crossbows and Handguns only need 3s to wound. But with dwarfs they need 4s, this makes a big difference especially when you have units with bows and slings which have a ST of 3 needing 5's to wound. Not only do the Dwarfs get have superior toughness than there rivals they also get out of action on a role of a 6. This makes dwarfs a enemy to be wary of, this advantage gives dwarf an upper hand that no other race has. Since you start off with a small number of units compared to other war bands this makes this skill very valuable in surviving. Also those war bands who start off with the same number of units of that of your war band are at the disadvantage. 
Dalkwave The Foreigner tips: 
"Beware of critical wounds. T4 still allows critical wounds to
S3 hits. And a lot of sling shots are going to cause that critical
wound for example. All Dwarfs start with 1 wound so OOC is close. 
Pistol range : The 12" range is not so
great (short range is only 6" still) but can be increased to 18" with
Eagle eye (a S4 short bow!). You can make better with the appropriate
skill and get duelling pistols (22" range). I'd say that the Noble and
Engineer are the only models that should start with a missile weapon
and it should be a pistol." 
Dwarf Leadership
There mighty leadership of 9 humbles even that of the Elves where only there leaders have a leader ship of 9. In the Dwarfs case all dwarf units except for the beardlings which have an LD of 8 have an LD of 9. This is another dependant advantage dwarves are dependant on. Due to there small numbers, and due to the fact that the game is heavily based on Moral checks and bottling out. There strong leadership of 9 have the highest probability of a unit running away or the war band bottling out.

Dwarf Weapon skill
The dwarves weapon skill is only equal to those of the elves, other war bands have a much more humble WS of 3. This is another tactical advantage, in where you need 3's to hit than 4's. 

The Enemy
1. will always use there numbers and agility against you
2. will try and get into to key position (such as position itself on a high building so the unit has better line of sight).
3. They will try and out maneuver you and flank you.
4. They will try and split up your forces to make sure minimum damage is done against them

Note: try and give helmets to as many dwarfs as possible, with a T of 4 and 6 for OTT plus helmet 4+ unmodified reverts a unit from stunned to knocked down will make your dwarves super hard!!!! 

DO NOT BUY ARMOUR AT THE START WAIT TILL LATER
DO NOT BE TOO COMPLACENT WITH YOUR DWARVES THEY MAY HAVE A T OF 4 AND ON A ROLL OF A 6 OTT BUT BELIEVE ME IT COULD BE ALL OVER IN 2 TURNS.

"Arrogance is woe of kings and the fall of Emperors" (quote by Sam Sedghi)
Respect the enemy.

Dwarven units

Dwarf Noble
An excellent fighter and a good marksmen, He is your leader and the center of gravity of your war band. Arm him with a Dwarf axe and if you can afford a pistol, give him one, if not them try to give him a pistol remember he's the only dwarf at the start with a BS of 4. The dwarf noble will have no trouble with dealing with enemy heroes, just make sure he is with others in your war band, the enemy will always try to use there numbers against you. 

Dwarf Engineer
A must have in any dwarven war band. The extra 6" range he adds to all the war bands missile troops is a vital weapon for the dwarves. If you can afford it arm him with a missile weapon if not then give him two hand to hand weapons. 2 attacks is better than one.

Troll Slayer
Ah my favorite of the lot, make sure you arm him with two weapons, this will come in handy once he gains certain dwarf skills. 
Dalkwave The Foreigner's tip: 
Master of blades with two Dwarf axes is the best combo you can get.
Thick Skull is something to consider to get some protection.

Dwarf Clansmen
A good resilient unit which can take many blows, make sure to give them two hand to hand weapons to make them effective.

Dwarf Thunderers
have at least 3 of this unit and armed them all with crossbows for now, later on if you can sell them and buy hand guns. these units will be your true weapon as positioning them in good key areas and it will lead you to win the game.

Beardlings
Start with them instead of Clansmen, much cheaper. Make sure you do not have any clansmen in the beginning, getting a dwarf with a T of 4 LD of 8 and BS of 3 for 25 gold crowns is a Bargain.

Weakness: expensive to start with and replace dead units, slow, have a terrible initiative. Small in numbers

Overall: try and start with at least 6-8 units if possible. Try and have at least 3-4 heroes at start cause you'll need all the money you can get. Don't forget lots of missile troops. Good luck!