I use two methods...if I'm tying buggers or girdle bugs or something similar, I'll tie in 2 or 3 pairs of legs sticking out the sides. To do this, strip two strands of rubber from the bulk of rubber (leave the 2 strands adhered together). Cut the desired length so that the legs extend out on both sides however far you want them to. Tie them in using x-wraps - similar to tying in dumbell eyes - and then pull the legs so that they are straight across the hook. Wrap your body, hackle, whatever, then peel the legs apart from one another. It makes wrapping around rubber legs a snap.
Another method I've used on spiders and big dries is to take one strand of rubber and fold it around the thread. Do this on both sides of the hook at the same location and you've got a nice X pattern to the legs.
Let me know if I've confused you with the rambling and I'll clarify. Hope this helps!