Well, there are certain drugs and things that people say make dreams much more vivid, but that's not really necessary. In terms of a vivid LD< I think that WILDs are naturally mroe vivid, as you're going straight into the dream with a much more 'conscious' mind, rather than a 'subdued' one...

As for all dreams, I've found that my dreams seem to be getting more vivid, or I'm just remembering them better. I think that getting into the habit of trying to remember your dreams will, ultimately, increase the vividness of them. Getting into the right frame of mind for having vivid dreams thats eem realistic and where you seem to make your own decisions. I think that remembering dreams and becoming more accustomed to them is a way to increase the vividness.