It seems that most of the time when IDs are talking about a project they consider Plan-Driven methodologies as their choice by default. However lots of ID projects have a Change-Driven nature. Seriously, except the "golden question" of "Who are your audiences?", I can not think of any other more important question than "Which methodology to use?" for a project start point.

Here, I am going to briefly compare the main two methodologies and to make a very quick cheat sheet on which one would be more suitable for the situation. Of course there are lots of detailed debates and many books and articles on this subject but based on my experiences this can do at least 80% of the job easily!

Waterfall, is a linear approach means a stage by stage approach for development. It is plan-driven with very low tolerance for changes in requirements during the process.

Agile on the other hand is a an iterative, incremental method, and of course more open to changes.