I'm picking up my prescription, first time I've ever gotten it

I have a date tomorrow, better to have and not need than need and not have mentality.

Looking for advice on what to expect - how it actually takes to kick in, how long does it last, do I need to let it wear off before I go out in front of children and old ladies, that kind of stuff.

I'm wondering if I should try a half of one tonight to get a feel for it, but with the date tomorrow, are there residual effects I'd have to about?

Thanks