I'm planning to hire a UX designer to create some wireframes for me, I am aware that he will need some detailed information about how i would like the site to work etc. To preempt his requests I'm wondering:
what would you require to begin wireframing a social networking site?
do you need user goals? design principles/guidlines? user experience flowcharts? concept posters?
Thanks for any help you can give.
Have a look at paper prototyping.
Once you have an idea of how the user interface should work from the user perspective, you can hand over the paper prototypes to your designer, or create a more formal specification.
As mentioned by Robert paper prototyping is a good option. You could make use of online UI Designing apps like http://www.balsamiq.com/ You could try it out online for free.
I know I am too late to reply this query but still if it helps...
If he is a UX Engg, explain your entire project and he should come up with few mockups. If he is a visual designer, you need to show him the mockups you have and he should be able to suggest you few designs to make it more appealing.