CleverPhD has great tips - and is 100% spot on with regard to establishing a connection first. I have found its vital to first establish a trust basis - proving through action that I am a respectful human being.
For me it starts out with social media - following someone on Twitter, sharing their content when I genuinely find it valuable, engaging in dialogue politely and not in a forced "doing this for a future link" manner, being helpful...
If I can connect with them at a conference or meetup where we both have a valid reason to be at the same place in person separate from "going there to get a link from that person", it allows the POTENTIAL for in-person real world reinforcement of that genuine connection.
NOTE - I have had people do that with me but then when they heard I was going to be at such-and-such conference, invited me to dinner. I played along out of respect, and it turned out they were just looking to suck my life-force, it wasn't as genuine as they led on to believe.
Don't be that person.
