of course best is after you "wake up" in the dream, then meditate. if you can do it the results will be ten times fasrer and more profound than doing it while awake. you will be meditating with the subtle mind --directly! a lot of waking meditation is towards just tickling the subtle mind a little bit.
of course get ready to abandon your foolish preconceptions of reality. if you have them.(most do, especially most on mudcat).
the inabiulity to abandon those preconceptions is what stops most meditative practice from progressing, and also stops real lucid dreaming --that is where you can actually controll what happens.