I would begin by forming a relationship with a photographer you want to shadow. By doing this, s/he will trust you to go on shoots, will value your insights, and will be happy to mentor you.
Definitely.
And this goes for anything really.
Find people that you respect and want to learn from. Reach out to them and offer to assist them. Be diligent and attentive if they allow you to assist them, but don't be discouraged if they don't.
Back in Pennsylvania, everyone was a jackass. There were people *looking* for assistants and I would respond, but they were threatened by me so they sent me packing. Which is ridiculous, because I lived in a different enough area, and didn't shoot the same way or have the same target clients, but that's how central, northeastern, and Philadelphia work so. Yeah.
But when I came to Nashville, people have been surprisingly helpful. There are still those here that will shut you out, but overall, the community is much more helpful and willing to foster new photographers.
That being said, my BEST connection ever made, was a connection I wasn't *trying* to make. At least not from a photography standpoint.
I met a guy at work, who intrigued me when I found out he was a photographer (and a good one, at that), but we ended up becoming really, really good friends. Because of that now, I assist him, and I learn a sh*tton from him. But not only that, he assists *me*... just because we're friends... and now that he's officially decided to launch a wedding brand, I have a secured slot as his second shooter.
There was no wheeling and dealing over it, it was just something he decided, based on how we work together and the fact that we're good friends.
Moral of the story is, reaching out and being persistent is important, but even more important than that is the relationship you build with that person, or anyone else you run into.