My recomneded changes to make this easier to read.
Welcome to my lockpicking guide. Please read the entire guide before posting questions. Very few questions are NOT answered in this guide. Thanks!
Q. How do I get the skill lockpicking?
A. A rogue trainer (a major city one) will give you a quest at level 16 that gets you thief tools (for free) and teaches you the skill.
Q. Okay, I have the quest, but my skill is super low I can't complete the quest, what now?
A. In the same area as your lockpicking quest, there should be some chests you can level up on. These chests are orange at skill level 1 (see below for color explanation) and don't go grey until about 100. Also, see down below for a 1-300 skillup guide.
Q. What do these colors mean? Red? Orange? Grey? I'm colorblind!
A. Every lock you pick has a 'skill level'. Just like with tradeskill items, they are color coded.
Red = can't pick the lock at your skill level
Orange = guarenteed skill up
Yellow = good chance for skillup
Geeen = low chance for skillup
Grey = no chance for skillup
There is a list down below for commonly items and their skillup numbers in reference to lock difficulty.
Q. Do I have to visit a trainer to get journeyman/artisan/safecracker rank in Lockpicking?
A. You don't. Your skill scales with level: every level you gain as a rogue translates into 5 extra points to your lockpicking cap.
Lockpicking Guide from 1-300
1-100 - Keep picking the instant respawn chests near the lockpicking quest.
100-175 - You can pick the Polly quest chest (not the instant spawn chests), OR you can use the chests in the Poison quest you get at later levels. You will have to click on your lockpicking skill first, then click the chest.
175-225 - Pickpocket mobs for Sturdy Junkboxes. Several mobs drop them, check thottbot and pick the best location for you. I recomend mobs in instances, that way you can pick it clean, reset the instance, then go to town again. You can also pick doors in instances at thie range. I personally picked the door in the Scarlet Monestary cathedral from 180-225 one day by repeatedly resetting the instance.
225-280 There is no real easy way that I've found to skill this range other than to keep doing junkboxes. You can use the gates in the NE corner of Searing Gorge, but there is no reliable way to reset them (see notes below for more information).
280-300 There are 3 doors in BlackRock Depths that are very close to the zone in that you can use to skill up this. Small note that there is really no reason to do this, because once you are at 280 you can pick every currently known lock anyway.
If your skill is lower than "orange" number, you won't be able to pick the lock (It won't even let you try). If your skill is higher than the "grey" number, you won't get a skillup from that item. A "?" marks information that might be wrong, multiple "???" mark missing information.
Battered Junkbox (Orange: 25? Grey: 100?)
Worn Junkbox (Orange: 100? Grey: 175)
Sturdy Junkbox (orange: 175 Grey: 275?)
Heavy Junkbox (Orange: 250 Grey: never?)
Dropped Chest - These are extremely random, so don't try to camp them.
NOTE: If you pick someone else's chest in the "Do not trade" window, you will NOT get a skillup, reguardless of color.
Heavy Bronze Lockbox
Ornate Bronze Lockbox
Iron Lockbox (Orange: 80? Grey:???)
Strong Iron Lockbox (Orange: 130 Grey:???)
Steel Lockbox (Orange: 175 Grey: ???)
Reinforced Steel Lockbox (Orange: 225 Grey: never)
Mithril Lockbox (Orange: 225 Grey: never)
Thorium Lockbox (Orange: 225 Grey: never)
Eternium Lockbox (Orange: 225 Grey: never)
Doors in the normal world (aka not in instances) are usually on some sort of timer. In other words, you can't repeatedly pick the same door over and over again for skillups. The mechanism of the timers are not well known. Some people say if you pick something else (anything else) inbetween attempts that it will reset some timers. Others say that if you pickpocket a mob, or kill a mob, or so something else, that this will reset the timers. It may be different for every door. Suffice to say that reset an instance always (to my knowledge) resets any doors inside, so use that method when you can.
Gnomeregan (Orange: 150? Green: 200)
Scarlet Monastery (Orange: 175 Green: 226 Grey:???)
Searing Gorge Gate (Orange: 225 Grey: 300?)
BRD (Orange: 280 Grey: ??? )
Scholomance (Orange: 280 Grey: ??? )
Small Locked Chest
Reinforced Locked Chest
Sturdy Locked Chest
Ironbound Locked Chest (Orange: 175 Grey: 250?)
Most of these are chests used in quests that you can pick after you complete the quest. Note that you will probably need to active your picking skill first, then click on the item as your cursor will not change automatically like it did during the quest or before it.
Insta-chests from respective lockpicking quests (Orange: 1 Grey: 105)
Main chest in lockpicking quest (Grey: 75/80? Grey: 175)
Poison quest chest (Orange: 90 Grey: 175)
Polly chest (Orange: 90? Grey: 175) (See note 5 below)
Engineered Practice Locks (Green: 1 Grey: 75) (You can only pick these ONCE, so they are WORTHLESS)
Cozzle's Lockbox (house by the Venture Co. STV, it's on a ~20m timer) (Orange: 150? Grey: 250?)
Links for lockpicking quests with respective insta-chests:
List of things that increase Lockpicking:
Dark Leather Gloves (http://www.thottbot.com/?i=5538
Various notes and other information:
Alliance rogues using the Klaven tower (Posion quest) chest: I just did this at 39, go to Westfall to where the poison quest is at, top floor, Klaven can take me down to half health at 39 if I don't dual-ambush so he kinda hurts. Hopefully you can also be outside his aggro range to practice. To do this just go behind his table (after he spawns he walks around the top of the tower, wait until he is done and ends up a bit away from you), there should be two chairs, jump over the chair closest to the chest and from behind the chair pick the lock. Don't worry about Touch of Zanzil: a death or Jungle Remedy from STV or cure poison from a high enough player should make it all good.
You must be of a high enough level not to aggro Klaven!
You can skill up 8 times on the doors to SM, there are 4 doors, 2 inside instances and 2 outside. They are on timers which can be reset.
(See confirmed information 1, above)
Only about half the chests are pickable and are trivial at 175.
Library: Chest in a cubby before the Gallery of Treasures, guarded by 3 mobs. Another chest that spawns in one of the hallways close to Doan himself, guarded by typically 2 mobs + one roamer.
Armory: Chest either in the Training Grounds (guarded by 2 mobs + 1 roamer) or inside the first part of the armory (guarded by 2 mobs + 1 roamer.) Can't remember location of other chest off the top of my head.
Cathedral: Chest on either the left or right side of the fountain. Another chest that spawns either by the monk guarding Fairbanks' hiding spot, or spawns on the other side of the cathedral (guarded by 3 mobs + 2 that roam close but may or may not aggro.)
South of Ratchet along the coast a short way is a beached pirate ship. No pirates around ship, they are camped south of it. Bit tricky getting the jump up onto the prow of the ship so you can get onboard, but can try repeatedly with no hassles. The chest is by itself downstairs in the back. Just keep opening it til you hit 175. No fuss, no muss and NO FIGHTS! (This is the location of the Horde lock picking quest and is in Horde controlled territory. Not recomended for Alliance characters on a PvP server).
I've left some stuff out I'm sure, but this is just what I'd do to better format the information.