Don't go in with any expectations. The ones I went to, there were no opportunities to slow dance (a little disappointing). Look appropriate (not slutty). Take things as they come. Your crush is definitely nervous too, if knowing that helps you feel a little better :) and then just have fun.
When its time for slow dancing, put your hands on his shoulders and and have him put his hands on your waist. Proceed with wobbling to the rhythm of the music. Make eye contact and you might get a kiss.
Yes don't push really hard down on his shoulder, keep a nice smile on your face, and try to talk to him during the dance. Ask him what he likes to do, his hobbies, and other things. And try to tell him a bit about yourself. Good luck 😉