There are two types of combat that I run. We will call them formal combat and informal combat, for semantic purposes. The goal of combat is to have excitement and adventure while not destroying the rest of the story. As such, we do a lot of things to keep it as short as possible.
Informal combat is entered into when the STs know that the outcome of the battle is certain. Fighting cops and elders are the two classic examples here. Also, some combat involving a large number of NPCs will be handled this way, since the PCs are generally too small a force to have much influence in the battle, even if they are evenly matched with a single person on the other side.
In informal combat, actions are abstracted. This means the STs might ask for general actions (for each round or for the whole battle), and ask you to roll something arbitrary to see how you do. It should be emphasized that while your actions may have no effect on the outcome of the battle, they will certainly have a great effect on the world after the battle is over. So if you stood toe to toe with Jan you might be looking at a point of courage and a one way ticket out of the city (or to Jan's solarium); if you try to spare the cops, your Humanity will thank you later.
Formal combat -- like Gaul -- can be divided into three parts in our home-brew system (which is always under modification!).
Initiative is always Wits + Alertness, difficulty 4, with Celerity adding +2 dice for each dot if it is being used. You can assume this is the case, so don't bother asking for difficulty.
To-Hit is always Dex + appropriate ability, difficulty 6, unless the STs tell you a different difficulty. In other words, if you don't hear a difficulty it's 6, so don't bother asking. This stage is not always needed depending on how close you are, the awareness of your target, etc.
Damage and Soak are always Str + Storyteller Modifier or Stamina + Fortitude diff 6. Again, it's always gonna be 6.
A word about the Storyteller Modifier. This is some combination of a damage modifier for your weapon and a bonus for a good To-Hit roll. Just trust us. No, really, To-Hit roll successes get put into Damage dice at about two to one. Stakes do one extra die, claws two, baseball bats two, swords 4 or 5, knives one, 500 year old two-handed swords wielded one-handed do 6. If you were curious. See the table at the end for the damage of common household items.
A word about armor. Standard light armor (kevlar and the like, non-hardened) typically provides two dice of protection vs. bullets, one dice vs. knives, swords, and claws (yes, claws), and zero dice of damage vs. baseball bats, fists and the like. Hardened armor (with metal plates in it) give you two dice of protection vs. all sources listed above. You lose an effective point of dexterity however. You should automatically add your armor to your soak 'cause the STs ain't gonna remember.
It's up to you to remind a ST of some special ability that might be applicable. We try to remember, but in combat it's really really hard.
Dodging is always an option. When the STs are looking at you the wrong way you can always dodge. This requires some initiative on the part of the player as we are often busy gleefully rolling To-Hit. If you dodge with all your dice pool your action for that turn is gone. If you dodge after your action one turn your action for the next turn is gone. You can dodge "on borrowed time" for as long as you want, but if you want to do anything else you are going to have to have a turn of inaction. A single action of dodging affects any and all attacks that your character can see/dodge against that turn. Dodge is always Dex + Dodge diff 6. You can not dodge if you are held down, being grappled, under a car, etc.
Celerity is a bit of a special case. Your first action will likely come before everyone else's. This is great for you. Your "extra" actions will come at the end of the turn. One of these can be a dodging action. There are occasions when you will not get one or more of your final actions. This is the penalty for having such a darn high initiative. You are prey to ST desires for drama. See below.
Certain actions end combat. When a NPC wants to be all noble and shit and say that you've won, or perhaps just heckle you and run, then combat will end then and there. This is often because the STs anticipate that the PCs will be happy with this result and are ready to move on with the game. This may or may not be the case. If it's not the case a new combat round will start and some PCs with low initiative or celerity may lose their actions for the turn that the NPC ended prematurely.
Location, location, location. Its often hard to know where everyone is in a swirling mass of bullets. We've been trying to use pizza box diagrams more and more which will help clear things up. In general, if something happens that doesn't fit your picture of where everyone is, just let it go. Ask for a clarification of where everyone is as soon as possible, but once something has happened it's generally too late to change it. Also, when describing your character's location many PCs (though actually not this group) tend to vacillate. "I'm keeping my distance ... but I'm not going to look like I'm keeping my distance." Consider vacillations license for the STs to decide where you are.
Creativity is greatly encouraged in combat. Many STs rule this differently. We like short and sweet creativity. Tell the STs what you are going to do. Don't write us an opera about it. And don't tell us what happens, that's our job! "I pick up the phone (you know, those old iron Ma Bell monstrosities) and smash him in the head." That's what we're looking for. "I wash the flames over his ammo." Never hurt to try. This is all very good. Remember that there are no hard and fast "mechanics" for creativity. Trust the STs to make things dramatic at the very least. Your called shot to the groin may or may not work, depending on a combination of ST fiat and some special roll. Remember that a single success is very marginal. If you want to make that called shot to the groin you are going to need at least three successes.
The areas of "creativity" that do have hard and fast rules are removing limbs (and heads) and staking. These maneuvers are only useful with certain equipment. Claws and swords are about the only thing that can take a head off (claws can do it for ookie supernatural reasons, not because of their size). Wooden stakes are about the only thing that can stake a vampire (funny, that). A sharp object to the heart does do bad thing to a vampire's blood supply, but only Cliff currently knows that (and he found it out the hard way I'm sure). In any case, these maneuvers all require the same thing, 5 net successes on the To-Hit (after dodge) and 3 net successes on the Damage roll (after soak). This means that they are very hard to do.
Once you've been creative, and in general at the end of every round, the STs will give a synopsis of what happened that round. You might not get immediate feed back on your staking attempt. For dramatic reasons, we try to pull it all together into a description of the whole combat each round rather than individual actions.
Finally, rules for some of the weapons the characters have access too. All damage is in dice except where noted.
Bat -- Str + 2 (bashing)
Stake -- Str + 1 (lethal)
Knife -- Str + 1 (lethal)
Light Sword -- Str + 3 (lethal)
Claws -- Str + 2 (agg)
Teeth -- Str (agg)
Torch -- 2 (agg)
Glock* -- 5 (bashing)
Tec-9* -- 6 (bashing)
AK-47 -- 6 (bashing)
Shotgun* -- 8 (bashing)
Dragons Breath -- 2 points (not dice) agg damage. Max range 20 feet. You can sweep over a bunched group of targets doing one point to each.
M-60 -- 12 (bashing) (for a 3 shot burst)
WP Grenade -- 10 (agg)
Bazooka/LAW -- 10 (agg)
(*: these guns have limited range)
Firing three shot bursts generally adds +3 to damage (To-Hit +1). Firing full auto adds +6 (To-Hit +2). Because of mechanical limitations in the gun you can only fire 1 3 shot burst or 1 full auto burst per turn of combat, no matter what celerity you have.