Can I come just once to try it, or do I have to take a course right away?

Of course you can come once and simply try it - the first session is exactly for that, so you can feel the method for yourself and decide whether it's for you. No one forces you to take a package right away. That said, to be honest: in one session you'll get pleasant relaxation and a first introduction, but the real result comes from regularity. That's why many people switch to a package of sessions after the trial - but that's your own calm decision after you've tried it.