I need to make edible tulle (the fabric netting stuff) for a wedding cake but I'm not sure how to go about it. Would the easiest way be to just do royal icing in a net like design?

If you need it to be flexible you could try sugar veil. I haven't used it myself but everything I've read says it would work for what you want to do but it is pretty pricey.

Sugar Veil -- it will give you the netting effect -- check out their website for info and photos of the technique

I just discovered sugarveil yesterday! Its freaking awesome!!!