What's you business? Joining SPE would be worthless for someone specializing in the auto industry.
Regardless of your business, I find that conferences have a really low potential to either start or advance a business--just too many distractions. I go to a lot of conferences either to present papers, teach short courses, or for my own personal development. It is amazingly rare for someone to contact me for work because of one of them.
On the other hand getting active in your local chapter of national organizations can lead to work. Attend every meeting for a year, get to know the people around you, participate in any fund raising they do. Then when you know the players see about assuming an officer role. This crap takes time, but it improves your network of people who might be in a position to use your business.
