Thought I would throw this up here, just to get the ball rolling. While I am a younger Beastlord myself, I have been progressing rapidly, and have a lot of background, having played since June of '99. So, I think I am capable of offering ideas of where to hunt for almost any level. Remember though, that a lot of where you can fight depends on your gear, and all these places and levels I will list are meant mainly for the soloer, or one who would like to take a smaller group of like-leveled people.
Levels 1 to 5. Newbie grounds are usually the best to just stay in, but obviously some are better than others. I find Everfrost to be my all time favorite place to level to 5, any character, any class. Just take the Pok Book to Halas, and you can pull things right to the book area. Pretty much anything moving is a good target. Since Everfrost is also now a Lost Dungeons area, helpful higher levels will often buff you, especially if you don't ask. Make sure you thank them though, and never beg. It's normal for the 4th and 5th levels to slow down a bit, but use the time to get all your combat skills as high as you can. If you are a Barb or Kitty, there are several merchants nearby, If you are evil, head back to PoK to sell your hard won booty. Save all those ruined Bear pelts though, they are great for tailoring practice.
Level 6 to 10. Paludal Caverns offers the easiest exp of any place, and is usually a good idea, especially for the soloer, as the mobs here do not hit all that hard, and have few hps. From Plane of Knowledge, take the Book to Shar Vahl, which will put you in Shadeweavers Thicket. Simply follow the road to the Tunnel enterance, and remember, make your first left, then a right, then another right to enter Paludal. Stay near the zone, and pull the smaller bugs to the corner. Turning OOC and Shout off are always recommended. Don't forget to go to Shar Vahl and pick up training and spells as needed. They like all races the same.. Apparently kitties in EQ, much like reality, are wholly apathetic to everyone.
Levels 11 to 15. Paludal Caverns is still the place to be. Follow the same route to enter, and follow the wall to the right, and you will enter a lower tunnel with Reishi's (mushrooms) and larger beetles to kill. Most things assist each other here, other than the mushrooms, so its usually best to kill the mob where it stands if you cannot pull them to some place safe. Respawns are fairly quick here, so you won't need a lot of spawns unless you are very well twinked. Don't forget to go train your skills, and it never hurts to just take a 20 minute break from killing, meditate, and chain cast spells on yourself to raise skill. Heal yourself with Inner Fire if you are hurt, it's far more efficient than minor healing.
Levels 16 to 20. Hope you aren't too sick of Paludal Caverns. 'Cuz that's where the best exp is still. Head deaper down, and start working on the Plerg Fiends. The new warder and its rather powerful lightning proc will make short work of them. Always keep cure disease up, and cure yourself of the crud the Fiends like infecting you with. It's not exactly deadly, but it is good practice no matter how you look at it.
Levels 20 to 25. Hey look, its.. Paludal Caverns. In no other zone will you spend so many levels. Be glad of that. There are other places you can go, but Paludal just is the best in terms of easy exp. Follow the ramp down some more, heading towards the main area and the camps. If you want to group at the camps, that's fine, but honestly, I would just solo, your skills will be all the better for it, since you will be practicing them far more. Head down from the Plerg's, and into the Patog's. As any RHPS fan knows, same mobs, different lighting. They will easily take you to 25, and your warder at 22 will shred them limb from limb. Make sure you practice all the skills you can, and med often. Every 10 points of meditation skill is 1 more mana per tick while meditating.
Levels 25 to 29. Yay! No more Paludal! While technically, you COULD stay there till 29, I really don't feel it's worth it, and your OOC and Shout channels miss you dearly. Turn them back on, and head through Shadowhaven and back to PoK. Where to now? Marus Seru is a great place now, as long as you learn how to avoid trains, and most importantly, where to set up camp so that trains aren't an issue in the first place. From the Nexus, Zone into Netherberian Lair (It's the zone to the left of the PoK Book), once in Netherberian, run through, hang a right at the giant pillar, and straight into Marus Seru. Now all you need to do is hang a left, and follow the zone wall to the zone area by Sanctus Seru. You will see a large hill on either side of the salty flat that serves as a path. I usually set up on the left hill (facing Seru) and pull mobs to my warder I have parked on the hill. Finding a partner of any sort is good here, and don't forget to practice those skills as much as you can.
I seem to be accentuating getting your skills up a lot here, and for a good reason. The experience in Paludal is actually too good, as you tend to level before your skills have a chance to increase as much as they would in say, South Karana. So you need to make an effort to cancel the negative out as much as you can. We already fizzle enough with our casting skills maxed. It's downright embarrassing when our casting skills are suffering horribly.