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?
Mine goes back a bit further. The first books I remember collecting was Thor right around the time that Hercules had an extended guest stint (I'm thinking around Thor 219 or so. (I think I a had a couple of scattered issues immediately before that). Not long after I picked up the Avengers and it was just as the Celestial Madonna storyline was about to start (I think I started around issue 126 perhaps). And at around that same time Marvel was putting out Marvel Triple Action and I started that on issue #20. It was reprinting old Avengers issues from around issues in the higher 20's with such tales as the Wasp being captured by Atuma, Pym becoming Goliath, then the whole Hawkeye/Black Widow/Red Guardian storyline, the Collector, etc. Dang, that was a great time to start reading comics.
It's been so long ago that I can't say for certain, but I'm pretty sure those old Marvel cartoons with the wonderful theme songs from the '60's(Captain America, Iron Man, Hulk) predisposed me towards Marvel books and Avengers related characters.