It started back around 2008, when I was about 5, my grandma taught me how to use her computer. I used to browse the net with her, check her emails, check the weather, find and play flash games, find answers to questions on indexed forums...
Then a friend's dad showed me youtube when I was like 6, I browsed around and checked out some songs and videos that were popular at the time, but not much more. I didn't browse the internet too often back in the day, but I do remember exploring around the computer, desktop, file system and the net as a kid.
My approach to internet culture definitely started with Flipnote Hatena, when I connected my DSi to the internet about a year before Hatena shut down. Memes, touhou, music, anime... It was like a mini version of the internet which was probably mostly controlled by 4chan at the time... And I loved it! Of course I still used to play flash games, send emails to some friends that had it, watch a bit of youtube... But it was mostly Hatena for me!
I started of super young, I know, and I actually do regret letting the internet raise me at times, especially when it went out of control back when I was about 12. No, with that I don't mean that I got on /b/ or anything of that sort, in fact, I never did. It's more of an obsession that I started having with the online world, online friends, y'know all that stuff, it was way too early for me and I'm glad I got out.
But honestly? At the same time, I don't regret entering here so early, because I got to have a taste of the early internet, and I loved that place of chaos, and I'll keep it in me forever.