Read original post by Paul Laberge at Canadian Mobile Developers' Blog
Part 2 of this 5-part blog post series on success strategies in the Windows Phone Marketplace deals with a fairly unique component to the Windows Phone platform called Trial Mode. If you make use of trial mode in your paid apps and games (and you really, really should if you plan on putting a price on your app/game), then you are making it much more likely that users will download your app and in response to that, make the possibility of them paying for your app much higher as well.