Crate Insurance Agent

Edit: As this is the top comment, for visibility purposes I'll try to keep it updated every day until we finish this achievement, because Wowhead is so slow to add stuff.

Here we go:

All the crates for Crate Insurance Agent and No Crate Left Behind

1. 
   
2. [item=232263]: Found by a Blizzard hint, in Desolace, you must be dead to see the crate and accept the quest.
   
/way #66 54.0 58.1 Desolace Crate

   
3. 
   
4. [item=226200]: In Zuldazar, buy a [item=225996] from [npc=143029] (on the sea floor) and interact on the shell above her.
   
/way #862 54.2 54.2 Zuldazar Dive Bar

   
5. 
   
6. [item=228767]: Pick up [item=228768] in Thousand Needles then buy the crate from [npc=91079] in Azsuna for 500g.
   
/way #64 66.3 86.2 Underwater cave entrance
/way #64 64.9 84.4 Water-Resistant Receipt

   
7. 
   
8. [item=228322]: In the Karazhan crypts (not in instance). Use the coords below or this video showing path to crate: https://www.youtube.com/watch?v=MxZ5GuOdPlI
   
/way #42 39.83 73.11 Step #1 Crypt Entrance
/way #42 33.52 70.72 Step #2 Go down the spiral tunnel
/way #42 30.22 81.33 Step #3 Swim to the other side
/way #42 22.43 83.74 Step #4 Crate location

   
9. 
   
10. [item=226375]: In Rivenwood, Howling Fjord. Use the [item=208092] to uncover it.
    
/way #117 29.41 6.36 Howling Fjord Crate

    
11. 
    
12. [item=228212]: Underwater, off the coast of Tanaris, south of the Caverns of Time inside a gnome building. Do NOT step on the elevator inside the building, it can and will likely crash your game.
    
/way #71 69.17 68.64 Crate (Underwater Inside Building)

    
13. 
    
14. [item=228976]: In Mount Hyjal, at the base of a trampoline.
    
/way #198 13.6 33.5 Crate in Mount Hyjal, at the base of the trampoline

    
15. 
    
16. [item=231886]: Grab the [spell=463368] in Ashenvale, this gives a 30 min Buff that can only be kept on Kalimdor. You will lose it if you port anywhere else. You must travel via non-loading screen means! Potion does have a ~5 min respawn so if not there hang out and it should come back. Then fly down to Feralas near Dire Maul area and grab the crate.
    
/way #63 47.9 38.4 Potion of Truth
/way #69 60.42 35.40 Mildewed Celebration Crate

    
17. 
    
18. [item=228983]: Inside Oshu'gun crystal in Nagrand, Outland
    
/way #107 35.27 74.81 Crate inside Oshu'gun in Nagrand, Outland

    
19. 
    
20. [item=228770]: First collect the [item=228772] from inside a cave outside Ahn'Qiraj, by the water. Then use them at the Unmarked Grave in Stormheim.
    
/way #12 40.4 93.1 Cave entrance in SW Silithus behind Ahn'Qiraj (not inside instance)
/way #12 40.7 92.8 Summon a dog battle pet (like Perky Pug or Corgi) to dig the Mysterious Bones
/way #634 37.4 47.6 Place the bones at the Unmarked Grave in Stormheim

    
21. 
    
22. [item=229367]: The crate can be found in Maldraxxus on the upper level of the Seat of the Primus, next to the portal that would take you back to the inner area.
    
/way #1536 49.99 73.81 Ghostly Celebration Crate

    
23. 
    

To see which crates have been returned, listed in the order of the table above, copy/paste this command into chat:
/run local s,t={"HAZ","SOG","SAN","DIR","BAT","WAT","CHA","MIL","CRY","SUP","GHO"},{85574,83794,84624,84470,83931,84426,84767,85523,84773,84625,84909} for i,v in ipairs(t) do print(s,":",C_QuestLog.IsQuestFlaggedCompleted(v)) end
Note: There is an alternate version of the #1 crate, which is only available if you did NOT pick up the Desolace crate. It can not be picked up on a character the [item=232263] was picked up on (so if you've been following this guide, basically too late now, must be done on an alt). It can be found at the following coordinates in Nagrand, also while dead (so drop down without armor on from a great height). Release, then click on the [npc=233545]. If you don't see it, you must have already collected the [item=232263] on this character, must be done on an alt.

/way #107 21 60 In Nagrand TBC - Fly up, dismount, die and release here
/way #107 21 57 As a ghost run around the mountain and interact with Curious Haze


Credit: WoW Secret Finding & Collections Discord server, channel #guest-relations-secrets

Crate Compilation:

Crate 1: After completing first secret questline talk to Alyx /way 63.02, 50.28, (shes in the big main tent), click through chat bubble, on the bulletin board behind her click the Damp Ransom Note. Travel to Zuldazar (BFA) /way 54.30, 54.53, (under water). Talk to Nikto, buy Clam Digger. Swim up to the big clam nearby, /way 54.26, 54.27, click clam, click chat bubble, turn in quest back at Alyx.

Crate 2: Travel to Desolace (Kalimdor), /way 54.0, 58.1, fly up in the air, drop from a high enough height to kill yourself, run back to coords, loot crate while dead.

Crate 3: Thanks to User Wario52. Travel to Thousand Needles (Kalimdor) /way 66.35, 86.14, swim down into the cave, pick up "Water Resistant Receipt" at /way 64.91, 84.45. It will be on the ground behind a large pipe in the cave. Then travel to Azsuna (Legion) and locate [npc=91079], she travels up and down the east cost of Azsuna (Legion). Buy the crate for 500g.

Crate 4: Thanks to User Wario52. Travel to Deadwind Pass (Eastern Kingdoms). Go down in the crypts at /way 39.85, 73.62, once down the stairs go straight towards the gray brick tunnel, make your first right, next turn left at the fork, go down diagonally across the dirt room towards the water, swim across the water, crate is in the far back left. /way 22.57, 83.64, is where the crate is.

Crate 5: Travel to Howling Fjord in Northrend (Wrath) /way 29.40, 6.43. Battered Celebration Crate will be there. If the crate was not made visible by another player, use your [item=208092].

Crate 6: Travel to Tanaris (just go to where the Anniversary event is). The crate is located at /way 69.18, 68.60. It is under water, inside a building. Go in, swim up the elevator shaft to the 2nd floor, and its behind one of the beds. DO NOT TOUCH THE ELEVATOR YOU WILL DC.

Crate 7: Travel to Hyjal (take the portal from portal island in Org or SW). Go to /way 13.6, 33.5. The crate is next to the post of the trampoline.

Crate 8: Travel to Ashenvale (take Hyjal portal in SW or Org, fly over), and go to /way 47.9, 38.4, on top of the mountain near Lord Magmathar. Click the Potion of Truth, this gives you a 30 minute buff. Travel to Feralas /way 60.42, 35.42. Loot the Mildewed Celebration Crate.

Crate 9: Travel to Nagrand (Outland). Quickest way is portal room (in SW or Org) to Shattrath. Go to /way 35.85, 67.20. Go all the way down to the main circular room. It will be near one of the big pillars.

Crate 10: Travel to Ahn'Qiraj: The Fallen Kingdom (take Uldum portal in SW/Org, fly west over to AQ: FK), /way 40.4, 93.1. Its a cave behind the raid, along the ocean. Head to the back of the cave, /way 40.7, 92.8. Bring a dog pet out (Perky Pug, Scout, etc.), loot the Mysterious Bones. Go to Stormheim (Legion), travel to /way 37.4, 47.6. Place the bones from your inventory. Accept quest, crate credit will be given to you upon turning in the quest.

Crate 11: Final crate. Travel to Maldraxxus (Shadowlands). I find it easiest to go to the portal room in SW or Org, take the Shadowlands portal, fly to Maldraxxus. The crate is located on top of the Seat of the Primus. /way 49.99, 73.81. You don't need to be part of the Maldraxxus covenant.

Per Blizzard this event will not start until October 28th Article Link

"Often a thankless job, guest relations has a new volunteer, Alyx, stepping into the role with the lofty hopes of doing a better job than their predecessor. As visitors pour into the celebration, Alyx is under pressure and could use a little help making it an event to remember. Thankfully, they have found a secret-sleuthing tuskarr family who have become the perfect helpers in getting players up to speed with the tools of the secrets trade.

Assist Alyx each week with resolving new guest mysteries by using your new secret-finding skills, and be on the lookout for stolen celebration goods. Follow the rumors and solve the mystery— if you can. We’re counting on you, secret finders.

Players can begin working on the initial secrets beginning on October 28 with additional secrets opening up on November 4."