The NPCs that do TM quests are Clerk Z, Keeper Julio, Love Hunter Robin, Monkey_T and Card Girl. They all have a little TM Bubble over the NPC. Keeper Julio can be hard, because you need to drill 100 of an item - but it's good experience.
They're should be at least two of these NPCs per area I think, likely for more though.
The Keeper Julio one is a daily and can be done well, everyday.