Currently Being ModeratedJan 8, 2013 7:27 AM (in response to D\'ox)
if you talk about default font on blank template then you may create new documet, edit it the way you want (set fonts, margins, language, etc.) and save it as template "Save as template" from Pages' File menu. Then in Pages preferences > general > For new documents set to use the template you just created.
Currently Being ModeratedJan 8, 2013 9:22 AM (in response to D\'ox)
A little more detail
You need to create your own default template. Open the blank template & set up your document with the line spacing, margins, headers, etc. as you'd like. Redefine all of the paragraph & character styles to have your desired font. You can set default wrap for any object as well as many other settings. Insert a table, click in it & choose the font, size, color, etc. you want in the fonts panel or format bar. You can do similar changes to inserted objects & text boxes. While you're at it resize the box if you want, set the amount of extra space in the wrap inspector, etc. Delete each text box, object & table after you've set them.
Now, save this document as a template & select that template as default in preferences. If you decide to make any changes to the template down the road, just Save As Template again with the same name & replace the previous version. All of your new documents will have these settings for inserted objects, images & tables. Unfortunately, the settings won't apply to any other templates or "foreign" documents you open with Pages.