Here is the list I use. Yours may be different. But you have to start somewhere, and you should have a list of some sort.
Mine is courtesy of http://www.greensmoothiegirl.com
Not allowed: white sugar, brown sugar, corn syrup, aspartame (Nutrasweet)
Allowed: real maple syrup, molasses, organic/raw agave, raw coconut sugar, dates, fruit, stevia, raw honey