Is it better to write "Related Work" at the start or in the end?
The main advantage of putting related work near the beginning is that it allows you to very clearly define what is new in your approach.  I like to do that when I'm attacking a very well-defined problem and my contribution is closely related to what has gone before; e.g., if I've modified algorithm X so that it runs twice as fast, then I must review prior work on algorithm X.  I try to work the review into the flow of an expository structure -- i.e., introduce prior work as you move naturally through the introductory and motivational concepts.

The disadvantage of putting related work near the beginning is that the reader must wade through it before getting to the important part of the paper -- your contribution.  It also may interrupt the flow of exposition.  So I put the related work nearer the end when possible; for instance, if I'm solving a problem nobody has considered before, or exploring some newly discovered phenomenon.