I start by picking and singing a song I know inside out, to warm up fingers and voice.

Then, I'll try one in a different key. I'll pick a couple of reels jigs or hornpipes each in a different key.

My version of scales, I suppose.

If I'm learning a new piece, I'll play it over and over until I've got it, then play it again.

If it's a piece to do on stage, I do it early in my set (like within the first 3 songs) to get the new-song butterflies out of the way.

I notice with some of the posters' practice habits that it would be difficult for them to play in a band, or professionally.
But if you're playing just for yourself, heck, anything goes!

Seamus