What is the sweet spot for experience gain? Is it more effective to fight the highest level enemies I can find, or am I penalized for being out of my depth? Are certain areas of the game better/best for experience gain/leveling? Are bosses better than areas with infinite minions? Would I get exp faster in a higher-level co-op game? What are the most time-effective techniques for rushing/boosting a character (either solo or co-op)?
Kill flesh stick again and again in the Tina special guest quest. best if your coop partner stays by her and keeps beginning the mission while you are where he spawns waiting for him with a shotgun or else. at lvl 14 its 1800exp every time. i leveled to 20 in 5 minutes.
Note: If you restart the quest too quickly fleshstick will stop spawning and you will have to reload the area. To avoid this, wait until Tiny Tina finishes her line ending with "my abode". If you mess up, first she won't speak her next line. If this happens, wait a minute or two (to let Tina finish the sentence, even though you can't hear it) and start the mission once more, Tina should talk again.
What I found interesting is if you kill one of the 3 Rakk flying around in vault of the warrior one will continuously spawn from a spot around the arena flying at you and attempting to attack you.
This becomes quite awesome because they do not stop coming at you, if you're prepared to stand on the spot (at the bottom of the stairs just before you fall into the arena is the best) for a while, it's good xp.
At level 50 playing TVHM they give you an average of 300 XP per kill. If you have adequate power in your shots or a good gun with a decent size mag they will drop like a rock. If you have the bee one hit or if not maybe from 2-3 or 5-7 depending on power of gun. This becomes around 3000 to 6000 xp if you can kill 10-20 rakks, in one magazine. So after only 4 mags you get the same xp as if you killed the warrior.
This is great for boosting another character, just throw him in your game and kill rakk with your lv 50 guy and xp is yours. It is a bit time consuming but not as much as other methods, and it's damn easy. About 20 minutes to get lv 47 commando to lv 48.
Hope this helps :)
Recently posted from Reddit - /r/Borderlands, "Easy way to level up any character":
In the mission: Rock, Paper, Genocide, Marcus makes you shoot a stat, vulnerable enemy. If you decide to shoot the enemy with the wrong elemental type, you still get the xp for the kill, and Marcus just spawns another enemy for you to kil! If you happen to have an Infinity Pistol or any other gun that rapidly kills, you can rack up xp VERY quickly.
You get most experience from the Bot target.
The fastest way to level is to level a seperate account on your xbox to 50 by whatever means you find fastest (I used warrior farming, or just playing through with second account on).
Once you have a level 50 on the seperate account, use that account to finish playthrough 1 and almost all of playthrough 2. Stop on the last mission (Talon of God) right before you call the moonshot to kill the warrior. Save the game and quit.
Now reload the game and a second account (most likely your normal account). Run down there with your second account, moonshot the warrior (25k+exp), collect the lvl 50 legendary that drops pretty much everytime, shoot jack (79k+exp), Pause the game with the second player (account your leveling, not the one with the quest) exit the game with that character which saves for only that toon.
Now with your first player (one with the quest) signout of your profile, this will take you back to the title screen without saving, allowing you to repeat as many times as you want.
You can level any new toon to 50 in about 1 hour, this is the fastest I have found without actually cheating.
On a second note, while playing through the game with that level 50, have a second person logged in as well, that toon will not only complete all quests, but they will also be around level 45 when your toon finishes the game.
Good luck and happy leveling.
There's a tradeoff between fighting very high XP gain enemies, and fighting relatively low XP gain enemies but killing them much faster. This break-even point tends to move as you level, so a general rule of thumb might be that if you find yourself getting knocked down often in an area, and/or kills are relatively far between, you're probably better off finding an easier area to farm in.
That said, I'll note a few areas I've farmed XP in, and some pros/cons to each. I used these methods to level 3 secondary characters up to the 20's while co-oping with a post-TVHM level 53 Axton in order to get character-related achievements.
In the Vault of the Warrior area, there are infinite numbers of Rakk that you can fight constantly. It's time consuming to get here, as you have to go all the way through Hero's Pass to reach the Vault. There are some pretty rough fights, including a Badass Constructor. You can run past these guys, but on TVHM with a level 53 Axton, I still found myself going down pretty frequently.
If you have the Torgue DLC, the Bar Room Blitz mission can be done over and over again for XP. Of the several repeatable missions in the DLC, this one seems to be the easiest and most profitable. The enemies here are always 50-52, even on Normal mode, so you'll want to be mid 50s in order to kill them fast enough to make it profitable. If you can't just wreck face on these guys, you're not going to gain XP fast enough.
You can go pretty much anywhere on TVHM and find enemies that are in the high 40's and low 50's. If you're getting kills consistently, you'll level quickly. It then boils down to where there aren't many annoying enemies that slow you down and give you trouble.
I personally prefer Arid Nexus: Badlands. There are JNK Loaders here, which are easy to cripple and kill. There are also a lot of skags, which are also easy kills. Second to this might be the Wildlife Exploitation Preserve, where there are many of the same enemies, plus some Stalkers.
Head to the Dust after completing the mission "The Good, The Bad and the Mordecai", you can then farm Mobley, Gettle and McNally (plus the Black Queen if you want). At level 26, the first 3 all gave 3.5k experience and had a chance to drop a unique weapon.
There are youtube videos showing the shortcut to get up to the church where Mobley & Gettle respawn. There are also a few weapon chests in those areas.
The best experience farm I've found so far is the Vault of the Warrior. You can complete it relatively easily at level 35 and power level any character you want up to 40 in relatively good time. After you've finished the game the first time (that is there is no Handsome Jack to deal with), you can just spawn the warrior and hide out by the map exit.
The warrior on TVHM will rack up experience but to get even more there are infinite spawning rakks but after a while of farming them the change to a different location.if not to high of a level I would farm the bunker with a good sniper rifle like the lyuda. Plus farming the bunker gives you a chance to get legendary loot and heads for your character.So good farming.
I found it was easy to farm the bunker on the second playthrough; get a high level person (I use the assassin with the sniper tree decked out) and go to Thousand Cuts. Join with the player that you wish to level up and keep him/her at the spawn point.
I use the assassin with the bee shield and a high level sniper and an infinity pistol to rush through the bots until you get to the bunker, spray him in the eyes and you kill him very fast, I end up doing 100k+ damage per shot, so spray 1 or 2 rounds into him and the second player receives around 25000xp each time and I receive an about $100k and around 10 eridium.
If you want easy experience, run Sawtooth Cauldron over and over with a lower level second player in co-op. There are about 130 enemies in this area. If you run it with a level 50 character to level up a second character, each enemy is worth between 300 to 2000 XP. This area is also great for farming badass points for your characters due to the high number of enemies that you can just run through.
Moonshot farming is the fastest way, though. 25000 XP every time you hit the button for your second character. Make sure you do it right though, because if you mess it up you have to start all the way back at the beginning to get a character back to that spot.