There are a number of websites that you can look at (google barefoot horse trim), and one that is often referenced is
Barefoot for Soundness
Keep in mind, though, that every horse's feet look different and there are many trimming philosophies, so don't expect that a good trim needs to look like the pictures. This may be too simplistic for many, but in my experience, if the horse is comfortable, the trim is fine. If the horse is sore or lame, then I would question the trim.