Attacking: Telling someone in DtD40k7e how you feel about them in five easy steps.
It's a page and a half of stepping you through how to hurt someone. With some examples and exposition. I approve of the examples, I just wish that some players would read them once in a while.
1. Tally up your modifiers and figure out what you'll be rolling.
2. Roll your attack. Base: level (if proficient) + skill rolled and skill kept.
2a. Victim may be able to stempt to dodge, parry, or take some other defensive reaction.
3. Hit location. 1 & 2 are legs, 3 - 6 is the body, 7 gizzards, 8 & 9 are arms, 10 head. I occasionally modify by critter body plan, once it was: 1 - 6 big long tentacles, 7 - 9 body, 10 plasma beam eyeball.
4. Roll damage. Remember any modifiers, and melee attacks add strength as rolled dice to the base weapon damage.
5. Apply damage to the victim. Armor on the hit body part, less the penetration of the attack, is subtracted from the damage. Then divide damage by resilience and drop fractions. That's you hit point loss/wounds taken. If you run out of hit points you go to the critical tables at a 1:1 ratio of wounds to critical level.

We had a guy who, for months apparently, without telling anyone was ADDING the penetration vlaue to the damage and then subtracting armor. Which would work as long as the penetration of the attack is less than your armor.

Any how, the biggest bugaboo of the system is resilience. The calculation to determine it and the damage divided by resilience. The outcomes are good, bigger things are easier to hit and harder to damage, but the math adds a good one or two seconds even once you're used to it. Sure (30 - (12 - 8))/7 & drop fractions is something 10 year olds do. But 8 PM Saturday night after a glass of wine and two slices of bad pizza, and you've been at this since 3 PM... Well, sometimes it does stuff to the mathamatic capabilities of even the best of us.

Of course just scribbling down a chart on the character sheet next to your hit point box solves 95% of the issues in play. Barring that occasional "count as a size smaller" stuff that pops up here and there. I'm honestly thinking that you could just run all those as "-1 resilience for this attack" or "+10% damage" and it would be about the same most of the time. One other thing I've considered is to make hit points the result of the current hit point calculation times the resilence calculation. You would have to figure out a new way to determine the critical hit effects and large creatures/objects would effectively take a hit because you aren't dropping fractions any more. I'd want to spreadsheet a comparison of the results to see what it looked like. The critical damage is still kind of an issue.

Next section - combat situations. Mostly just various conditions and modifiers. It would be nice if these and some others were stuck on one big list like the actions were. I have something like that in my personal reference sheets but I've been thinking it needs to be updated now that I've run the game and have a better idea what gets loooked for often.

General to-hit modifiers
Combat advantage: +5 to get hit. Difficut terrain: melee attacks and dodging are at -1k0, or -2k0 for waist deep stuff and slick ice. In melee: shooting at them takes a -10. Extreme range: -15 to hit. Long range: -5 to hit. Point blank range but not in melee: +2k1 to hit. Short range: +1k0 to hit. Melee from higher ground: +1k0 to hit. Ganging up in melee: +1k0 to hit, +2k0 if your side outnumber the other side by 3:1.

* Cover: Acts as a layer of armor that has to be penetrated before damage can get to you. So it covers some of your hit locations instead of giving any defense bonuses. There is alittle chart from pipes and armor-glass at AP 4, through computer banks and static pods at AP 12, to plasteel walls and spaceship bulkheads at AP 32. By the rule anything penetrating the cover or barrier reduces it's AP by 1. Once the AP reaches zero the cover is destroyed. In my games I've done 'makes a very small hole' (it went though after all) and reduced the AP by it's multiple of penetrating damage. Ok, example: Someone wearing mesh (ap4) is standing off to one side in a submarine hatch (ap16, head, right arm and leg, and body #6 are exposed), with a static defense of 20. Three people shoot bolter rounds at him, rolls 15, 25, and 35. 15 is close enough to hit the hatch even if it wouldn't hit him (flip a coin, roll a scatter die, it's explosive bullets in a submarine, it goes somewhere). The 15 shot: AP 16 - penetration 6 = AP 10, damage rolls 7, 7 is less than 10 and it does nothing. The 25 shot: target dodges & gets 14, adds 7 to static defense and reaches 27, the round misses but check for a hit location anyways, if it was an exposed bit the round goes flying past, hit location left leg tags the hatch again, same math as last time but this damage roll is 18, 18 is more than 10 so 18 - 10 = 8 damage went through but still missed the target. Hatch AP is now 15 because something penetrated it. The 35 shot: no dodge so roll hit location 7 = gizzards, AP 15 - penetration 6 = AP 9, damage roll explodes all over the place and gets to 42, 42 - 9 = 33 damage gets through, target's armor takes off 4 because even though the bolt round's penetration is 6 it got applied to the cover, target gets a 29 damage hit to the gizzards, 33/15 = 2.whatever so the hatch loses 2 more AP bringing it to AP 13. I generally apply breaches to about a square meter for small arms, 4 square meters for nasty stuff like lascannons, and whatever the blast radius is for explsions.
Concealment: For when you can't see the target very well. Usually a +5 to static defense but the DM can rule it to be more.
* Falling: 1 wound per 2 meters. Acrobatics + dexterity DC 15 to reduce by 1 wound and reduce by another wound per raise. Dropping or jumping down gets 2m per dot of acrobatics that doesn't count as falling.
* Two weapon fighting: Works about like you'd expect, you can get an additional attack with the second weapon when using the multiattack action. Both attacks at a -3k0 penalty, reduced by 1 die for having ambidexterity, reduced by 2 dice for having the TWF feat. Because it's a multiattack you have to spend that extra reaction to get the extra attack. You can stack TWF with the other multiattack feats.
Weapon jams: Takes a full action to clear the jam, dumps the ammo so you have to reload, tech use + intelligence or level + ballistics vs DC 15.

Ya know, next up is injury, healing, and critical hits. I'll skip that for a but and cover the conditions. That's just my personal organization style.

Conditions, again just interesting stuff because things like blindness are pretty obvious:
* Amputated limbs: Starting with a good one. The crit tables include limb removal. This is a game where "It's just a flesh wound." is a thing. Hand: -2k1 for two handed stuff. No holding. Potential -2k0 for the primary that you can buy off for 200xp if you can't snag the ambidexterity asset. Strapping a shield to the lower arm is OK. If you lose both hands: "she should either secure a replacement or get someone to sharpen her teeth." Arm: Same as hand but no shield strapping spot. Apparently losting both makes it difficult to reach hard to clean places. Eye: -2k1 sight bases stuff and half range for ranged weapons (since that modifies accuracy). Foot: Half speed and -2k0 for movement actions & checks. Losing both: "Perhaps the ship's Engineer has some spare wheels laying around..." Leg: As foot but no dodging, a 'half the person he was' joke.
* Blood loss: This is more than just a bleeding finger or something, it's a full spurting artery type thing. Each round roll 1d10, on a 1 you die. Medic DC 20 to fix, DC 30 if you're running, fighting, doing heavy lifting, etc.
* Dazzled: -1k0 to everything except sight tests, those are -2k0.
* Diseased: DM discretion.
* On Fire: At the start of the next and subsequent rounds while exposed to !!FIRE!! (or on a flamer hit) dexterity save vs. 15 or catch on fire. You can take a full round action to put yourself out, same save. DM modifies the save by situation (I give +10 for spraying yourself with a fire extinguisher). Being on fire gives you a wound and a level of fatigue each round, it doesn't say when so I'd put it at the start of the character's turn because I'm nice. If it matters this is usually run as an energy thye hit to the body unless a specific body part is on fire or something.
* Fatigue: You can deal with fatigue level up to your constitution. Over that and you're knocked out. If you have any fatigue you're at -1k0 to rolls. Fatigue heals at one level per hour of rest or relaxation. If it knocked you out you wake up in 10-constitution hours with fatigue equal to your constitution.
* Helpless: Autohit plus roll damage twice and add.
* Pinned: Willpower save DC 20, or DC 10 if you're no longer being shot at, roll again each round at the end of your turn. People in melee are automatically freed from pinning (too busy to care about getting shot at I suppose). If pinned: 1) Only take half actions, no full actions. 2) Must stay in cover or move towards cover. 3) May retreat away from the source of pinning fire if there is cover available there or if there is no cover anywhere at all.
* Restrained: +1k0 to attack rolls and may be immpbilized if the legs are affected.
* Stunned: Grants combat advantage and take no actions. Still aware and not helpless though.
* Suffocation: Hold your breath, if you even need to breathe, for constitution minutes or 2x constitution rounds if engaging in strenuous activity. Also make a constitution save DC 10 or take a level of fatigue every minute/round. At the end of your time you go unconsious if you still can't breathe. If you're unconsious and can't breathe lose a hit point every round and die at zero hit points.