It’s usually best to join one and get a feel for what they are like first. You usually need quite a lot of experience with regards to how a VA runs, what people look for in a VA etc. For no I suggest joining a small regional VA. One that comes to mind would be EuroManx Virtual. It’s a thriving VA and they are all friendly guys.
http://www.emxvirtual.co.uk
Regards
Marc Lennox