For what it's worth, it is relatively easy to do a constrained falsetto. Don't. More important than in even regular singing is to open up. If you try and control falsetto with the throat, you will very quickly tire out your voice.

Imagine having a lot of space in your head, and fill it. Then imagine filling the space in the room. Keep everything open. Once you have the falsetto, start at the top and gliss down into your chest voice. Pretty soon, you should be able to do the reverse, and connect the head voice, chest voice, and falsetto.

If you need someone to sing with, get a copy of Pete Seeger doing Wimoweigh, and sing along with the falsetto descant. This WILL annoy your roommate, so be kind.