Depending on the subs you buy, look in the installation manual. It will give a simple ported or sealed box design, usually with a round port, simple enough to make, and it's the ideal tune/volume for the sub, as recommended by the manufacturer. Another option is a pre fabricated box, which everyone on here will bitch about, so don't go with a best buy one for instance, but check around on the internet, there are a lot of boxes available, just make sure you choose a decent one, like one recommended by the sub manufacturer. Everyone is so against pre fab boxes but the truth is if your completely new to this, you'll probably be better off with a professionally made box.
There's a lot of differences between a pro-SHOP built box and a prefab box.....if you can find a local shop that builds a quality box; they can do it too... But it's gonna cost a premium price....