Blizzard luckily made leveling lockpicking 1-300 a relatively painless process in Vanilla World of Warcraft. Here’s the least headache inducing method for leveling your lockpicking:
Guides for thieves who dwell in the shadows.
Where is the entrance to Ravenholdt located in Vanilla World of Warcraft / WoW Classic?
How can rogues autoloot while pickpocketing in Vanilla World of Warcraft / WoW Classic?