Some journals provide class files and article templates for prospective authors, so possibly a good place to start would be to have a look at the submission guidelines pages for various journals.  [Geometry & Topology][1], for example, provides a [public class file][2] (which gives very similar results to the ones we use internally for producing the published versions) and an [article template][3] along with a page of LaTeX [good practice][4] advice and recommendations (more detailed documentation [here][5]).  The template file is probably a good place to start, but will probably need a little alteration if you're using it for a different class file.  (Alternatively, a web search for "LaTeX article template" should turn up something.)

Edit: Oh, I see.  In that case, I guess you need to write a LaTeX class file which mimics the current journal style.  And exactly how you go about that will depend on what the journal currently looks like, but I'd be inclined to start with a class file that gives almost the desired results (the basic article.cls in the absence of anything more suitable) and then start tweaking it until it looks right.  Your original question seems to indicate that it looks a bit like the Notices of the AMS, but it doesn't look like they make their class files publicly available.  Be warned also that some serious TeX hackery (HaXery?) will probably be involved.

The other thing to bear in mind is that if the production processes are currently built around a system that isn't LaTeX then you might have an uphill struggle persuading the editor and production team to switch, unless there are clear and obvious advantages to doing so.  (I speak as someone who once wasted several weeks attempting, unsuccessfully, to convince a dyed-in-the-wool Fortran 77 programmer of the benefits of object-oriented programming.)

  [1]: http://www.msp.warwick.ac.uk/gt/
  [2]: http://www.msp.warwick.ac.uk/gt/macros/gtpart.cls
  [3]: http://www.msp.warwick.ac.uk/gt/macros/gtlatex.tem
  [4]: http://www.msp.warwick.ac.uk/gt/about/journal/latex.html
  [5]: http://www.msp.warwick.ac.uk/gt/macros/gtpartdoc.pdf