Rendering Tips

Another thing is to add another layer and fill it with a contrasting color (i.e. if your original BG was white then use black) this will make the edges you may have missed stand out. You could also repaint the edges if applicable...say if it is a vector or something. Simply make your initial cut, duplicate that layer and then repaint the top layer. No need to try and get it perfect, just make sure you paint the edges and not into the render. Then load the selection of the bottom layer (non-painted), invert the selection, select the top layer (the painted one) and delete the extra color....that is a pretty long method but it ensures no "white" marks.