I generally don't grind for experience in games unless the combat itself is somehow mechanically fun or satisfying -- not something I would necessarily credit Stone Soup with, and certainly not NetHack. The closest I've ever come to grinding in NetHack is when I meticulously search the level for secret doors -- sometimes because I can hear a shopkeeper counting, and I want to find the shop, but most often because I've finished exploring the level and I've still not found the stairs down. Farming experience isn't the point there, but I'm sure I sometimes collect a bit extra in the process (searching being the time-consuming chore that it is). But, to be honest, I don't even recall the respawn rate after clearing a floor being that high in NetHack. Maybe it's just been too long since I've played it, though. :)

Late addition to my previous answer, but I can't believe I forgot this one:
Nightblair mentioned autoexplore, but neither of us mentioned the related search & auto-travel functions. Basically, you can search for items/altars/shops/etc. that you've already encountered, anywhere in the dungeon, and you'll be given a list of relevant matches, any of which you can fast-travel to (actual fast travel, mind you, not what amounts to teleportation). You can also simply specify a level of the dungeon (or any of its branches or sub-branches) which you've already visited, and auto-travel there, too. This uses the same pathfinding system as the autoexplore -- not perfect, but pretty damn useful.
I also just remembered another important one: shops are not rooms with an actual NPC shopkeeper, but instead act more like vending machines or something. Sort of. Anyway, the other key element of this is that you cannot sell items. At all. Which, like the "minimal grinding" aesthetic mentioned by Nightblair, is aimed at reducing tedium (no feeling compelled to collect every piece of junk you found on the first three floors to haul down to the shop you found on the fourth floor to sell). Basically, if you're pretty sure you're not going to need an item, you just don't pick it up. It does really help with inventory management, I admit. =)

Good point. I think this is the best UI features I've seen in roguelikes. Really, coming back to nethack UI after playing DCSS is... interesting eye-opening experience.

I'm actually kind of scared to keep playing my current (main) run in DCSS.
I've gotten appreciably further than I ever have before: I've fully explored and cleared at least 11 branches (plus poked my head into the Slime Pits before deciding, "Nope!"), as well as at least one or two of the random "catch it before it's gone" zones; I've gotten 4 runes so far (and that'll probably be it); I've hit the level cap for my character level and about 3 of my individual skills; my Minotaur Fighter has been extremely lucky with regards to finding good gear (some fortuitous finds early on -- plus the fact that, for once, I actually kind of babysat my skill training -- made it a cakewalk, except for a couple of touch-and-go "1-vs.-many" situations); and I've probably played somewhat more carefully than normal -- at least, after I started blowing through branches that have always killed me before (Elven Halls and Shoals) and realized I might have a real shot at getting somewhere.

But...I'm overly curious. I couldn't entirely resist checking out someplace where I probably have no business going, given my currently excellent chances of ascending successfully with the Orb. So, I decided to try a ziggurat that I found amongst the treasure in one of the rooms at the bottom of the Tomb, my rationale being, "Well, I can leave any time I want, since there's a portal out on each floor." Unfortunately, the most recent floor I cleared (9 or 10, I think...out of 27) was tougher than I would've liked, and I seriously doubt that was a fluke. But the "One more floor! Just think what treasure there might be!" impulse is strong.

Shall I cut and run, and just go straight for Zot, the Orb, and escape? Will I be able to drag myself away from the dangerous allure of the ziggurat (and Hell, and the Abyss...)? Tune in at some indeterminate time in the near future to find out!

Have you already won the game? If not just grab the orb and win.

Ziggurats can be quite random in difficulty, epecially for melee dudes. You can take usually the first 7 levels or so quite safely but monster density winds up pretty fast and despite an exit being on every floor you can die there really fast. I mean - really fast. As a MiFi you don't need the experience there and it seems like you already have quite good equipment so there is really no reason for you to be there.

Some branches (like Tomb) will almost certainly kill you the first one or two times you are there until you are knowing what you're doing.

It always depends on your character but for me with melee fighters the easiest branches of the extended game are usually Slime and Abyss. But if I were you I would just go on to Zot and win the game.

No, I think the most runes I've ever gotten was 2, and I'd never been to the Depths before, nor survived very far into the Vaults (or the Shoals, for that matter).

Yeah, that's what I figured. :(

First time in the Crypt and the Tomb. Crypt was absurdly easy, and even the Tomb wasn't too bad until the bottom floor...though there was definitely a bit of retreating and resting going on throughout. (Of course, my maxed-out negative energy resistance AND magic resistance probably helped more than a little. =D )

I was worried about mutation in the Slime Pits. When I was considering whether I should try to explore that branch, I only had one or two cure mutation potions stashed for the endgame. (I had recently used one curemut to cut down on the amount of negative mutations I'd gotten while using a couple of those aforementioned awesome pieces of equipment -- I got two different really good artifact axes (quite a wile apart, but still) that each had the *Contam property, which causes high-level magical contamination when unequipped. I actually didn't even notice the first couple mutations as I got them, simply because it apparently takes a while for the contamination to actually trigger a mutation (which makes sense, I suppose, since that gives one time to drink a cancellation potion or something), so by the time I decided to quit using the *Contam items, I already had 4 malmutations -- nothing truly debilitating, but still). So, I didn't really feel like facing potentially more mutation, and acid (which, to be fair, I have a ring I can swap in to mitigate if necessary). But I'll keep that in mind for future runs. :)
(I have since found more curemuts, BTW, but I'll save them for Zot and the run up.)

Another thing I feel I should relate: one of those awesome items that I found (NOT one of the *Contam ones) was an artifact +18 medium shield which also granted MR+ (maybe even MR++ ? I forget) and a couple other nice things. Unfortunately, the artifact name ended with "of the gong", which means that every time I blocked an attack (and with my already-high shield skill, the ridiculous enchantment bonus on the shield, and the amulet of reflection that I eventually found, I was blocking A LOT of attacks), it made a horrendously loud noise that alerted almost everything on the level possessing working auditory sensors, drawing them toward the commotion. Needless to say, from whenever I found it mid-game, to when I finally decided it might be more of a liability than an asset in the late game and swapped it for a more boring shield (after the Tomb, certainly, and after clearing most or all of the depths), I was fighting a large majority of most floors' denizens before having explored more than perhaps a third of a given floor's area, at most. (Of course, some floors are designed specifically so that happens no matter what. ;) )

Slime actually isn't a place that you want to explore, since there is literally nothing else than one bad guy (probably two if you're unlucky) guarding loot piles and the rune at the bottom of the pits, so you just dive down to the bottom - staircases are usually in sight. The only mutators found there are shining eyes, which don't show up in large groups and are quite fragile, so if you have a decent ranged option you can take them out quite fast. In general you should not be worried too much about mutations outside of pan and probably abyss. For slime you may need two cure mut or so, for zot most likely none (since the game is won anyway when you reach the point at which you will get mutations there) - but you can of course keep one or two for zot as well if you want to feel safe or for the case that you get a few of the *really* bad mutations very early.

More important for slime is corrosion resistance and mr, though.

Yeah, Gong shield is one of those artifacts in the game that you don't want to wear regulary. It's a bit like playing Qazlal without the benefits of worshipping him (and he is still a god that you don't want to choose if you want to win the game!)

Nah, Qazlal is fine, I'm not that good player and I chose him because I've been curious and still won with him. The cloud is powerful. I remember it was different experience than normal playthrough. I've stepped in the level and all the monsters in the level were going to the stairs because of the incredibly loud thunderstorm around me. So when I've dealt with them, the rest of the level was usually empty. It was all about causing biggest mayhem.

Nevermind, wrong game.

What is IAP?

In app purchase. Also, I was thinking of Pixel Dungeon, as it turns out. And the 5000 variants.

Ah. Well, there are, apparently, some Android versions of DCSS, though I don't know how good they are as ports.

Qazlal seems like a good god for tanky fighter-type characters (like the one I'm currently playing). The noise of the storm he creates around you (much like the noise of that shield I was using) means that the character had better be good at absorbing and/or blocking and/or evading damage, and fighting off a constant stream or large horde of enemies nearly at once. I've messed around with him before, but never seriously/successfully.

I've indeed had a shield, so I was good at blocking most of the damage.
If I remember correctly, the key was having high Invocations, so I can use also other destructive powers of Qazlal. The groups of monsters huddled together were actually to my benefit, as one of the powers is dealing damage around you, so I had not engaged in melee, but constantly used that Qazlal powers to destroy the mob. The more I killed, the more I could use the power that kills many at once.