Oh gosh, let me see... it was when I was a mere boy. XD
I believe my first anime was either Outlaw Star or Tenshi Muyo.
As I said, I was a child. Probably when I was around 9 or 10.
Although looking back, Outlaw Star wasn't the best anime...
However I still watch it and Tenshi Muyo every now and then for nostalgia.
Afterwards I became engrossed in the amazing Toonami lineup including:
Cowboy Bebop, Trigun, Inuyasha, Rurouni Kenshin, etc etc.
Oh gosh, I would be so excited coming home from school to watch afternoon anime.
Good times, good times. (Even better times when all my friends got into anime)

Funny thing is that my cousin introduced me to my first manga.
I was probably 14 or 15. I didn't even know manga existed.
(So many wasted years, but like with anime... I was hooked)
She plopped down next to me around Christmas time and handed a volume.
The manga was Fruits Basket and gosh, was it a difference to what I liked.
At the time I was into adventure anime about magic and knights, etc etc.
To be wooed by a very feminine manga... well it opened my eyes to a lovely genre.

Oh but anyways, I am ranting.