***** SPOILERS ALERT - MANY GAME MECHANICS DISCUSSED *****
Didn't want you to think that your post went unread.... Haven't answered because I'm not much of a deep diver, i.e. I don't specifically start every game with the thought of going really deep. If the luck rolls my way and I get great equipment / buffs or a good drop from my bones file from the previous game (see more on this below) I'll generally switch from amulet grabbing mode to deep dive mode.
What kinds of things would you like to have for a deep dive? This is probably going to be personal for every player, as everyone has their own play style.
Re: special characters - absolutely a good way to start off, especially if you're newer to the game. I like Athena and Ripley (their starting attributes can be found here: viewtopic.php?f=2&t=39
). Athena's automatic scroll identification is very handy in the early game, and Ripley's clairvoyance is great the whole game through, which is great if you're a stealth player. But remember - a secret character won't get you on any of the leaderboards (except for Secret Character, of course, but depth isn't shown on that one): http://bestrogues.chronosoft.com
My personal preferences -
** A magical warhammer (preferably Fire, but Holy is good too - don't remember if Holy weapons glow or not like Fire does, which adds an extra block of visibility around your character). The more powerful the better, especially if the to-hit bonus (the first + number) is 4 or 5, which means that the magical part of the weapon will fire 40-50% of the time on a hit. I like the warhammer most because it's a good balance of base damage and the possibility of knock back.
** A ring of slow digestion (at least one, two is better)
** Preferably a ring of searching - not required, but nice to keep yourself from falling in pit traps and away from too many poison darts (although, sometimes falling into pit traps can get you out of otherwise impossible to continue situations during *really* deep dives...)
** I'm a stealth player, so in a normal amulet run, I often go without wearing any armor at all from Floor 12 on (unless I've found some Shozoku or normal leather (not studded!) armor that I can pump up with lots of Enchant Armor scrolls). (If you're not sure why wearing no armor can be a good stealth tactic, try it and see what happens!) In a deep dive game, however, high + armor is an absolute must no matter what style you play.
** Enough Gain Strength potions to get me to into the low-to-mid 20's, and a half-decent stock of Restore Strength potions to recover from poison dart traps.
** As many sources of Paralyze as I can scrape together, the more the better (FYI, this includes food rations, which will put everything except Vampires to sleep - and then stealth is key so that you don't wake them up!).
** Some source of ranged attack capability. Buffed arrows or bows are handy here (especially if they're magical - magical arrows stack, so when you find more plain Jane arrows they become "guilty by association" magical arrows!). Often, though, this is a set of 2-4 additional war warhammers or battle axes - something to throw at powerful creatures that are down range.
Everything else is up to the luck of what I happen to have on hand and find as I go.
Specific game mechanics, "abusing" the system, and you:
This part is either going to be really helpful to you, or sound like a really cheap way to put together really deep dives (ie. cheating). Every veteran rogue-like player has (usually strong) opinions on these topics. For super-deep runs (floor 200+) some of this will become necessary, just because the difficulty ramp-up is so severe.
** Secret Character - again, perfectly fine to use, but won't get your name on the shiny leaderboards.
** Manipulating the starting inventory - If you're using a normal character, continue to restart games until you have a ring as the additional "random" item in your inventory. Depending on what ring you start off with (once identified), continue with your game or start over again. (Note that by doing this you're basically foregoing bones file farming - more on that next).
** Bones file farming - This is a method whereby you (hopefully) build up powerful weapons or armor (or both if you're really lucky) by intentionally dying, and then killing your skeleton on the next run to (again, hopefully - it's not guaranteed) recover and continue to build the strength of the weapons and armor. If you've ever played any of the Shiren the Wanderer games, it's a similar mechanic, except that in those games the ability to do so is intentional, whereas here it isn't.
** Wraith abuse - This one takes advantage of a bug in the game that's never been fixed. When wraiths remove a level from you, they 1) take you back to needing only one XP to get to the next level (usually the one they just removed), and 2) generally also remove a smaller amount of Max HP then what you'll gain when you defeat the wraith (and, obviously, level up). So, do this with enough wraiths long enough, and you'll have a most unnatural number of HP. I've seen HPs in the low 1000's. The challenge with this one is, if you screw it up, you'll lose more than one level to the wraith and wipe out a good chunk of what you're trying to accomplish. (I'm personally not a fan of this one, as it relies on a bug rather than on design decisions by CD.)
** Level dancing - By far the most useful suggestion in this list, and at the same time, the most controversial among long-time rogue-like players (and pretty much a requirement for super-deep dives).
Here's how it works: the amulet doesn't just appear on the 26th floor *but every floor below that as well*. The amulet's sole ability is to turn stairs that go down into stairs that go up (in this game - in other rogue-likes the amulet generally has additional powers). Also, once the amulet is picked up, it can be dropped (not all rogue-likes allow this, to prevent just this sort of thing from going on). Lastly, except for food rations (and even those are rare), on your way back out with the amulet you're not going to find any additional items to bolster your inventory - items other than food ONLY appear (with super-rare exception) when going DOWN.
So, go as deep as you're comfortable (but, obviously, to at least the 26th floor), then grab the amulet and head back up. You don't have to go all the way back to the first floor (although, if you burned a lot of your inventory making it back out, you should probably cut your deep dive aspirations and just take the win). Then, drop the amulet and head back down again - guess what... items appear again! So, collect as much stuff as you want, and probably deeper then the first trip down. Then back up. Then back down (even deeper). Rinse and repeat. The all-time mark used to be in the high 200's for deepest floor, but I'm pretty sure that others have made it deeper and just not reported it here on the boards.
You'll eventually have a choice to make if you're looking to get your name on the leaderboards. You can gun for the Wealthiest Rogues list (which never resets), which means you need lots of gold, but won't also get the benefit of winning (i.e. you must die to make that list). Or, you can go for the Amulet - Richest list (which updates over a rolling 30 days), but you can say you went deep AND won the game. Your choice.
My personal opinion on using these tactics? Since the game doesn't prohibit them, I'm fine if players use them; so it's up to the individual player. Not using them provides more of a challenge. Not using them means it will be that much harder to make the leaderboards (if you're in to that kind of thing).
Whew! This is a really long post! So... any questions?
Also, any actual regular deep divers, feel free to post thoughts here as well.