Short answer: Forgotten Halls.
Long (ok, long LONG) answer... I'm bloody old school. Played in 99 (not P99), within a couple of years my friends had all long since moved on to better things. I got to 50 just when they raised the cap the first time. I took a break, playing other games until about 06 to 08 when I decided to try MQ2. Back then, there weren't alternative communities (or I either wasn't aware or didn't have trust). You compiled the code (hell I even dabbled with assisting with offsets). I was writing most of my own bot-types even though there were some bots out there. I didn't trust them, and knew I could write my own. None made notoriety, nor did I submit any. I was mainly relying on events and telnet as I had a Unix box on my network. My bots would broadcast things like 'Report' and all toons would respond with current HP and mana, then some code would decide to either pull or wait another rest cycle.
There were no mercs, so you had to group. I would put 3 to 4 toons together, including a healer. You can start FHalls at lvl 15 however I have found that the mobs spawn low (too low) until 21-22. FHalls is an instance zone that spawns (ish) according to your level (or grps lvl). It's an 'expedition' off of Nedaria's Landing. The instances last 6 hours. I would setup an instance before work, after work, and before crashing for the night, so 3 a day. It isn't fast compared to what others have posted, but I didn't know of any other way. I had heard of bone chips, but feared it was too public. In hindsight, pre-nerf-nerf, it woulda been worth it regardless *shrug*.
It takes just over a week to get to 75 (1 1/2 weeks?). 70 to 75 gets slow, good time to max AAs tho. Even though it's slower than many other strategies, it allows you to max your skills along the way so your toon isn't gimped when done. With
MQ2Melee, you can set and reset (say for a monk) various skills to level up and they almost keep up with your exp progress. Now, it was always understood that after 55, if grp'd, the mobs would start to socially aggro (attack one, get 2 or 3). Otherwise, it's a safe place to level since you have your own instance (privacy-security), mobs are not aggro, and not social, small camp. You have to be cognizant of pathing though, say trying to run between rats and bats is impossible using MQ2 due to numerous ledges and angles on doorways etc.
Today, with mercs (and KA YAY - should fricken send Mas $100), you can solo from 22 to 75 (again 70 to 75 is slow). The rats or bats don't socially aggro if you are solo/molo so you can go beyond the 55 mark. The mobs spawn in 5 level increments, but not quite evenly divisible by 5 (mod?). What I mean is, between 21 and 26, the mob lvls are pretty constant. At 21 they are DB, White, and Yellow, so 20, 21, and 22. However they stay that range as you level until you hit the next 5-lvl increment (in this case 26) when they will spawn 25, 26, and 27 etc ad nauseum. This is AFK leveling folks. You have to occasionally get food and water (I had a DRU bound at entrance filled to the brim with iron rations and water, various Distillates (like alacrity, skinspikes and clarity). The loot is crap, you will get defiant armor for the lvl-range down from you just like everywhere else, and more than enough plat to handle your merc and any other expense. You'll make about 16pp a kill at least at the higher lvls (well, probably avg 5 to 10pp cause the 16 plat'ers aren't constant).
You have to restart the instance to get the mobs to spawn at the next increment higher if you lvl into the next range. Being 6 hour intervals though it kinda takes care of itself. I have recently used this method to raise a DRU, WAR and MNK to 75 so I can start a multi-box army. My mains are only 86 (old world SHM and heroic wizzy) so they will catch up quickly in Undershore and Icefall Glacier (which btw is worthy of mention - never ever saw anyone else in IFG). After the 06-08 MQ2 exploratory mission (damnit - almost a big word) I hadn't played until early this year. Again, YAY KA!!! Should kiss Mas right on the fuckin lips!
Ok, couple of misc things: set your pull radius to 100 'cause even if you have your MobsToPull ini set to rats, bats, you aint gonna cross over the hall between them. Haven't tried the mesh and
MQ2Nav... Don't forget archery or throw, you can keep those up as you lvl. Use
MQ2Melee for various skills and/or discs (when you get them) but realize, ppl often tell you to
/melee save and
/melee load but they don't tell you why. The why is,
MQ2Melee gets bloody wonky if you don't. You can have certain skills set to on but some wont fire. Save and load peeps, save and load. If you want to skillup casting skills, use your KA ini creatively or you will have to skill them up afterwards (but melee skills can keep up with your lvling as can your main casting skills).
I hesitated to mention FHalls. It was a closely guarded secret among early adopters of MQ2 back in the day. This is a public-ish thread (just create an account?) and I didn't wanna draw any attention to it (although, as previously mentioned, there are way faster strategies now).
I avoided big words, left out any techno-babble, but damnit if it isn't coming across dry *sigh*. Fuck the typos, Ima leave em.
--- Edit ---
After a 6 hr session, check your bags. Godamnit if I dint fill up on bloody Innoruuk arrow hats or the ova-infused Erolissi Mar ornaments. And now the fuckin shamrocks! Use the /lootdestroy function peeps if you want your bags clean, it sets the ini once and for bloody all. After about lvl 60 or so you will start to rack in gems so have an extraplanar (but you have to plop at least one of a particular type in it so it starts stacking). Remember to use Scribe (should send him $$ too) to quickly obtain spells and discs between runs, I'd suggest every 5-10 lvls. Use the Magus to get to Nedaria's Landing, I can get new expedition and run back to stone-in (haha) in my sleep, no really, done it while asleep.
--- Edit ---
Keep thinking of more things... The mobs max at lvl 65, so getting to 70 is pretty easy but that's why it slows down 70 to 75. This is however a great time to pick skills that haven't been maxed as mobs will be LB. You can also consider dropping healer merc at this time since you will be taking less dmg, especially if you have upgraded your gear, at the cost of merc AA. At 71, using a merc since earliest lvl, I had 10 merc AA on my monk. Turning it off will cost a couple of points not gained, not sure how many...
This is good to about 60 (maybe 65).
