Bokeh is the term used to describe the out of focus highlights. At a lens’s widest aperture, the bokeh is usually circular. As the aperture stops down, the bokeh usually becomes more hexagon or octagon like.
I use the Cokin P filter system. Having seen “Creative Bokeh” kits – I have decided to create my own - by using pieces of cardboard slotted in my filter holder.
I start by cutting out pieces of cardboard with the dimensions of 84×84mm. Then I draw diagonal guidelines, and then my shape, which is then cut out with a craft knife. I use it with my 50mm macro lens, due to it's wide maximum (F2.5) aperture. Here is the lens's natural bokeh:
These are some of my more successful designs.