I can get back to you with specific measurements for the fabric we have in stock right now tomorrow if you like. However I will say it definitely depends on the denim you have typically been wearing. We are more of the vanity sized variety, meaning a waist "size" is often going to measure a bit larger. For example our 30 will often times measure about 16 inches across the waist, making it a 32 inch waist.
As far as the stretch goes, I would always suggest buying them slightly more snug than you wish for them to fit in the end. A lot of people suggest sizing down in a more extreme manner, but I don't think it is that necessary. In my experience, the tighter the jean, the more it will stretch - but that doesn't mean you have to get it super tight or anything. For example, I could wear either a 30 or a 31 depending on how I want that particular jean to fit. Sizing down will keep it more slim/snug, but a 31 would still fit me appropriately.
I would expect about an inch or so of stretch in the waist, and some give wherever else it feels snug.
Feel free to shoot me an email and I can send along measurements of what we have in stock currently -> DH@BALDWINDENIM.COM