According to the tenth edition of The Gregg Reference Manual by William A. Sabin, under the heading Prepositions, Words Requiring Certain Prepositions (1077 page 300): "Usage requires that certain words be followed by certain prepositions.
Different from: This product is different from the one I normally use.
Different than: I view the matter in a different way than you do. (Although from is normally preferred, "than" is acceptable in order to avoid sentences like 'I view the matter in a different way from the way in which you do.'"
Note that "than" comes after "way" which answers the question: different how? See how much easier it is to choose the correct preposition in this sentence by answering the question first. This was indicated by a previous hubber.
Of course there are ways through and around the grammar mindfield. Change the wording completely if you're not sure, i.e. This is not the way I view it or I'd like you to consider this view point (product) or This one is not like that one because. You can pretty much twist and turn words every which way and still say the same thing. The idea is to get it correct no matter which way you choose. Using the word "differently" (adverb) is one of those twists you can use when you don't know or are not sure if it's "from" or "than." Of course differently would not be followed by from or than.
Whether it's this book or one of the others mentioned previously, a top-of-the-line grammar book is a must have for every aspiring writer or anyone who wants to get it "write."