Ask HN: How do I get more help from my coworkers?

As a new hire at my company, my productivity is mostly determined by how quickly I can learn the new system. Of course this means reading lots of source code, but sometimes the fastest way to figure things out about the company's system is to hear it from my coworkers.

However, developers tend to be extremely busy and are usually very hesitant to spend time pair programming or teaching best practices, even when asked. What are some things I can do to convince them to help me out?