Duplicate the layer your working at (I had masked the lilly in the front, and used the rest of the picture as my background layer), then apply a filter to it. For this ray effect, I used radial Blur, and the zoom effect. Move the center of the zoom effect to where you want the rays to shine out from. I dragged the slider almost ALL the way up, and then applied (if I remember correctly) a overlay to the layer. You can experiment with the different layer types, Lienar light might give an interesting effect too. then play with the transparency slider till you get the effect you're looking for. You might have to use more than one layer, and use different layerkinds; dodge, screen etc. Hope this helps. :)