Glyphs will also be saved with your 2 different specs. So different glyphs for the 2 different spec. So only will have to buy glyphs once for each spec.
"Nethaera: Will you be able to change your Glyphs as well? Ghostcrawler: Glyphs will be tied to each talent spec so that if you switch between them, so too will the Glyphs. You’ll notice the UI will have changed a little bit so that the Glyph panes show up alongside the Talent panes now that they are associated. " http://www.worldofwarcraft.com/info/underdev/dualspec.html
Here's a basic explanation of how dual specs work.
A) You start off untalented B) You spec like you normally would for your main spec. C) In your talent tree, just like you would spec your pet, there is a new button to view your seconday spec. D) When you click the button "Activate these talents" It switches your glyphs and talents to your secondary spec. Starting off, it is untalented. E) You then spec/glyph your secondary spec, and when you want to change you click "Activate these talents" again to switch to main spec.
Each time you switch it takes 5 or so seconds to cast, and resets your mana to zero. As well as triggers global cooldown.