I would first think about what criteria I'd want my own clan to have or what interests me. Most clans are a group of guys that have been playing through numerous COD games and have established themselves already. Since you're just starting out, I would try using search words that best interest you. If the clan name is something you can relate to...leave them a message asking for an invite or complete an application to the clan.
Or...you could just create your own clan with your own band of brothers.