First of all, make sure your scales are clean! A good scale scrubber will get you looking shiny in no time. You can find scale scrubbers at most magical apothecaries.
Second, don't forget about your horn! A good horn polish will make it look like new again. You can find horn polish at the local SparkleMart.
And finally, never underestimate the importance of good mane maintenance! A well-groomed mane will make you look like a true magical creature. Find a good mane stylist at the local Unicorn Salon.