Rev's comment below that Avengers # 300 was his first issue got me thinking: How did Marvel snag us, and get us to buy more of its interconnected universe?
For me, it started with Iron Man # 225. Perfect starting point, the first chapter of Armor Wars. From there, I moved on to WCA, since he was a member of the team. I got there just in time for # 37, which split the team up as Hawkeye & Mockingbird fought over the right to let a villain die.
About a year later, for my 13th birthday, I got a gift certificate to the local paperback store ... and went nuts. I bought Daredevil # 262 (part of Inferno), Cap # 349 (the penultimate chapter of John Walker as Cap!), and ... oops, Rev, it may have been Avengers # 299, as part of Inferno.
But I guess what really got me was Uncanny X-Men # 241. At 13, there was nothing to draw me in better than Maddie Pryor, spread eagle in her mini Goblin Queen outfit. I read that issue over and over, and picked up every issue since.
So what's your story? How did the Marvel marketing team get you to branch out and buy not just your first comic, but begin to sample their other titles?
I'd gotten a few comics previous to this, but Bill Mantlo's Hulk run had the then-current Avengers lost in time with the Hulk rescuing them all from the Leader. My mom picked me up the issue, and I was in AWE of seeing these diverse heroes, especially Iron Man. So a few months later, I got a few issues of Iron Man, starting with #168 and Tony's drunken rampage against Machine Man followed quickly by Jim Rhodes replacing him in the armor, and the Avengers issue where the Plant Man replaced Ronald Reagan with a tree-replicant and Iron Man resigned from the Avengers and Starfox joined. After those, I got seriously hooked... and was heartbroken when I moved shortly thereafter and couldn't get more books! I got a few haphazardly over the years afterward, including the West Coast Avengers #1, Vision and the Scarlet Witch #1, and a few others, but wasn't really able to start regularly back in until around Avengers West Coast #49. I haven't stopped since.