Especially if you want to insert more variables from the MetaData category (which is the one which stores all fields from File, Project Info) I would suggest two practical tips:

• Use guides to define the areas where you’ll insert the variables. They will help to keep that area free when adding content on slides.
• Do not forget to edit the length of the variable when inserting it, because for some variables the default length of 50 is insufficient.
• If you want to be able to control the visibility with actions of those variables placing them on the first slide, timed for the rest of the project, always on top is a good idea. But if you want them on all slides, I always put them on the main master slide, to be inherited on all daughter master slides.