Johnnypanic's write up is about as detailed as you can get (rate up!).
Many of the facts stated apply in general and not just to Paludal --something to keep in mind. Also, by character #4 I need a different levelling route to stay interested.
Kurn's Tower is fantastic using the same tactics 7-15. No runners if you stick to the skellies. With temperance you could go in lower.
Crescent Reach bats & skeletons on the top floor are great xp to about 14. That's pretty convienient if CR is your starting city. The undead in the rest of that same zone can take you to 18-20 pretty fast.
Shar Val 1-5 is stupidly fast too. Many don't realize there is a newbie area in the pit that surrounds the city. With skinspikes you'd be level 5 very fast. The challenge is finding the level 1 spikes.
As long as
Lake of Ill Omen is a hotzone it is worth the run. When it isn't... probably not if you goal is fast levelling without high level support.
Echo Caverns (the low side with the mutants) was a challenge in its day, now 20-25+ here would be fine. High magic resists and some runners, lots of adds. But with temperance and spikes your aren't worried about that anyway.
Needlites and Boglings are always an option if mutants don't work for you or your chosen class (results will vary)
Najena is listed as a 20-35 zone. I've seen people using modern tactics in there around level 12. They run, they cast, its a linear dungeon with keys you have to pick up. If a player is new to the game its a good spot to learn how to play beyond being massively geared/buffed beyond the content and pretending to be a tank.
Gorge of King Xorbb is listed as level 10-25. Again, you could go in way earlier if ready. No casters here except the evil eyes, but you are wearing defiant and will resist almost everything they cast. A level 65 ranger can barely keep the spawns down in this zone so levelling up is fast.
If you do it long enough (and don't touch the goblins) you will faction up and be safe to run into Runneye and sell and bank (you can bank even when KoS... but then you have to avoid or kill goblins). Sure the muddites and minotaurs run when you get down to the last one. Just pull multiples of the same race to lessen you mob chasing.
If you don't have spikes and the gear, this is still a great zone for young kiters. The zoneline into the karanas is a really long straight line that only one muddite seems to spawn/wander in.
The Warrens is great. Listed as 5-30 it not efficient XP at the top end of that, but it's fun in the teens. They almost all hit gimp, they
add like mad and you get funny faction ups (you do want to buy your own hole key and hang out with the intelligent folks in Erudin no?).
Gulf of Gunthak is listed 35-50. Go in there at 25 if you have the gear, 30 if you think you are weak. One side of the beach is undead if you hate runners. I've levelled characters in the tunnel of plants and drogmors... used to confuse the people trying to train through to Dulak (added risk for me)when half the cave was empty.
The Hole has the highest XP mod in the game. Assuming they take the end-game cliknars back out of it after Underfoot's launch, it is a great place to level for the mighty and brave.
Overall, my point is don't discount other zones. Easymode can apply to nearly every zone before Planes of Power on this
list on Alla depending on your ability to handle casters and adds. Even
Plane of Hate tier 1 is pretty tame and easy (wouldn't suggest Fear or Sky as fast levelling places though).
Edit: typos
Edited, Nov 7th 2009 11:07am by snailish