The only real thing that you need in order to have a "bed partner" as I call it is (drum roll please)
Honesty... I know, it sounds crazy right? Just bare with me.
Honesty in this situation is the best policy. In order to have someone be a bed partner, you would go through all of the steps that you would go through with a girl, except a few things.
1. Don't call this girl as much, because there's no need.
2. Almost all of your conversations have to have sexual undertones to them, or just be about sex period, which means that you have to find a girl that is more than comfortable talking about sex, having sex, and sexuality in general.
Also, keep in mind that you will have to develop a lot of sexual chemistry with this girl, after all... that is all you want. A bed partner is not something that can be done with just anyone, and oftentimes it is a lot harder to do in HS... but it can be done (believe me... I've seen it done, and if I wasn't for my schizophrenic morals... I would have had one too) I must warn you though: more than likely this girl will have to be a junior/senior... because you know how little girls can be. Now back to the honesty part, don't give her the run around or pretend that you really like her. Remember... girls often use sex to get love and that's not a place you want to be in. So just be honest with the chick, and tell her the real deal. Either she'll say yes or no.
There is no spoon...