Making Your own Units

I see all sorts of gorgeous printables and units on the various blogs that I visit.  They are intricate units and simple printable that look absolutely gorgeous.  My question to you is how??  Where do the graphics come from so that you can give away your packets or even sell them.  How do you make sure that you aren't copying someone else's idea?  I would love to start doing this for myself so I guess I am asking.. where do you start?

Please share any ideas you may have.  If I can learn how to jump into this great trend I would love to share my own ideas with all those that have given me inspiration.  YOU!

Watch for my next post on the classroom environment.  I am reading Teaching With Intention and want to share my ideas as well as yours!