It's simply about repetition. Baptism by fire is the norm for me, as I attempt to do newer songs live that I've just not totally memorized. Sooner than later, you will remember them in order to stave off embarrassment.

I do use the PA800 screen for my lyrics 'cheat sheet', but always have the arrangement memorized completely.

The more jobs you play, like anything else, the more you will remember the songs by heart. It's really not that difficult.

I played a private party at a Doc's house last night and their 7 year old was playing classical on her piano by MEMORY