First off, rules:
1. In order to get into HR, you will need to be below the citadel (on weather it'll show as yellow, not red or purple) and go up,yes. If your HPs are too low, you won't be able to go in (kinda cool!)
2. When you are in, you will end up in a random spot in the citadel. Find the red # - those are stairs up/down.
3. Forms almost always will meet on the bottom. On that lowest level, instead of the down stairs being signified by a red #, it'll be a yellow * and the room will be called "a way out."
4. The ways to get out of the citadel are - (1) walk out, (2) die to zombie and corpse, (3) die to Hellreaper and he will drag you out, but you can be iced meanwhile.
5. To kill HR, you need to have killed at least 20 zombies. If anyone attacks him without 20 zombies, he will hit really hard and reset a person's souls to 0 (doesn't have to be the person with less than 20, just anyone in form, one per round). So never attack below 20. People will be extremely angry at you if you do.
6. There are always as many zombies in the citadel as there are people in it (but there may be more outside, not sure). I don't know if there is a minimum number of zombies, that's possible.
7. SR/traps don't work. They won't do anything at all (won't damage you either).
8. Zombies see invis.
9. Feel free to use trip/bash, and can use eles if brawl situation arises.

Leading:
1. Use listen to find zombies (check that it's enabled in setcomm). It'll tell you where else there is movement (zombies, players, etc).
2. Have people BS or engage zombies, preferably with triggers so they don't walk past you. When they wimpy they'll rest so follow them and ice them. HR may run away on wimpy rather than rest, just fyi.
3. Careful with engaging more than 3 at a time. It's definitely doable but since you very rarely tick in HR, watch mana.
4. Set macros for farsight. I use ee nn ww ss uu dd. I've seen people use hn hs he hw hu hd, or do something else. But it helps checking rooms faster and moving around.
5. Zombies spawn on any random floor (I think there are a total of 6). By basic probability, if you clear the first 3 levels, chances are there will be more zombies above you than below (the zombies that spawned there + roughly 50% of the zombies that respawned). Based on the danger level, figure out if you wanna go up or down.
6. Note the level hellreaper is on, but also note he can switch levels (using stairs). He runs fast too.

Rushing
1. If you're rushing and you think your opponents will run out, have form phase, get in, and get to bottom asap. Try to hit trips there or nearby (you don't want people wimpying down but if that's your only choice, oh well).
2. If you're rushing and you think you'll have a fight, there's 2 places you wanna get together - either top level stairs, or the stairs right before the bottom level. If you rush to bottom, you'll probably get hit there and since everyone gets in at a random spot in citadel, you'll be trickling in.
3. If you're getting rushed and you wanna fight, your best bet is to just go and tick somewhere. If you wanna get out, though, run down to bottom but carefully. If there are below at *, wait somewhere else meanwhile.
4. If you're getting rushed while fighting stuff, a good idea is to flee and meet all the way on top, or at some spot on your current level.
5. If you're getting rushed and you're at 19+ zombies, I'd say just finish it. It's hard enough for them to find you, especially all of them. If you're quick, you'll be fine most likely. And even better, if you see someone on a random level, hit them. Their form shouldn't find them very quickly.
6. Very important - as people rush, the number of zombies increases accordingly. Very often in reaper brawls I see people dying to zombies. Watch out for that.