I just read a great post called 25 Absolute Essentials for Networking Success.  The whole list is great and I highly reccomend reading it.  I think the biggest lesson I learned in networking is at the top of this list and is something I learned the hard way.  The time to start networking is when you don’t have a need.  It sounds weird but it’s true.  When you are out of a job and have a need to build a network, it is not very easy.  In addition, it takes time to build a network so the best time to start is yesterday.  When you are gainfully employed and happy, that is the best time to start.  And when you need to call on your network, it will be there.