For me “technically” my first experience was back in closed beta. I was active in some cosplay communities back then and a friend from one of those forums, who I knew IRL from University, had got into the closed beta and wouldn’t stop raving about it. I tried the beta a few times on their PC.
As for when I really started playing, it was just before the Opening of the Gates of Ahn’Qiraj event started. Said friend had bought the game so I borrowed their game discs to test it out on my laptop. Needless to say my laptop wasn’t very great, it struggled to run at 5 fps on the lowest settings so as soon as I entered Ironforge I ended up in the infamous lagpits! In the end I ended up spending my entire spring student loan installment on a new PC (I justified it as being able to do my essays from home, but the reality was it was just so I could play WoW), and spent a good few months living off beans on toast.
I’ve told this story many a time, but I’ll tell it again. My first ever character was a Human Warlock, and I remember questing in Elwynn Forest and seeing a Night Elf Hunter who was using a fairly standard cat from Darkshore as their pet, and I was like “I NEED ONE!” I found the Cat Vendor in Elwynn and begged my friend for some silver so I could buy a kitty. I summoned my new feline companion and went around killing Murlocs, Kobolds, Gnolls, and Defias, and eventually noticed that the kitten wasn’t leveling up or attacking things. That’s when my friend told me that only Hunters could have animals as pets. I was so upset at the time, but funnily enough I didn’t actually make a Hunter until Cataclysm.
Moral of the story, we were all newbies once!