Tabletop greenhouse

I'd like to build a simple tabletop greenhouse / terrarium? -- maybe 12 x 24 inches or so with some flourescent lighting.
My question is this --
How do you determine the size of the openings to ventilate it?
Is there a specific formula based on cubic feet, etc?
I would imagine it would depend on plant size/species etc but just a good rule of thumb thing that would be good for everything from seedlings to maturity.
I just want to grow simple plants like Basil, etc.
Also place holes to the top or bottom or both? (bottom inlet -- top outlet?)

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.