Do I need a certain stamp for my mailing campaign?

[Benjamin Blackburn]

Hello all,

I will be doing my very first Direct Mail campaign next week and I'm wondering if there is a certain kind of stamp I need to buy?  I noticed on the USPO site that there are Forever stamps, Additional ounce stamps, postcard stamps ect... I know this is probably a dump question but I just don't want to purchase the wrong kind.

Thank you very much!