Using what version of FileMaker?
If this is Filemaker 11 or earlier, enter layout mode and select a font from either the formatting tool bar for from the appearance tab in the inspector (or from the format menu if version is older than 11.)
This then sets the default font for the current layout only (best we can do here)--until you start selecting different fonts/sizes and then, mysteriously, the default settings may change and need to be reset.
Often, it save a lot of fiddling to set up a single layout with one example of each type of button, field, etc and then copy and paste your layout objects from this one example layout, repointing the fields to the correct field after pasting.
In FileMaker 12, these settings are largely controlled by the currently specified Theme.
Sorry - FM 12.
So I would have to set a default theme?
You cannot set a default theme. You can select a theme for a layout and this will set a number of default formats for new layout objects that you might then add to your layout.
That is horrible. I would really like to not have to select a theme every time. The odd things is, there is a default theme, you just can't select what it is...