This is one of the strategies that I use in my journal article writing workshops. I ask participants to talk about the contribution that they want to make. Not write. Talk.

People talk about what they want to do before they begin any actual planning.

This seems to be a helpful way to proceed particularly for people who are less experienced in the standard journal genres. Talking gives an additional opportunity for thinking about the what, why and how of the paper to come.

I also often get people to analyse journal articles as part of this process. Read and then talk  is the order of the day. You can see how this goes in these recent writing slides.

http://www.slideshare.net/patthomson/talking-the-contribution-of-your-paper

See also these posts on contribution:

Defining a contribution

Using meta commentary to specify your contribution

Paper, thesis and book titles

And on talking and academic writing