Cultivating relationships with professors beyond your advisor I am a PhD student and I'm interested in pursuing a career as a professor upon graduation. 

I am interested in cultivating relationships with professors beyond my advisor so I can actually have other people to write recommendation letters for me when I go on the job market.

How can I best go about with this? That is, what are good pretexts for me to approach other professors?
Take classes with them. Go to their seminar talks and ask questions. Attend any social gatherings and chat with anyone you're interested in. Read their papers and drop by their office with a couple of questions.