I am getting some new tubes for my amp, and I want to do a 24-hour burn in. How?

Agree with mapman- why waste tube life- you don't put your car on rollers to bed the tyres in, you just take it easy for a while or end up in a hedge.

Keep a diary of hours and perceived sound if you're that anal unless it's the istant gratification of a bedded in system you're after.

On, no signal needed, 60 hrs, burn-in is done.

I bought tubes from Brent Jesse. 

Did NOT like them. 

He said, ok, finish burning them in, then keep or return them. Top line were his instructions which I followed.

They did change slightly, I still did not like them. I picked another I knew I liked (I had used spares of them), half the price, full refund (I paid return shipping)

Sounded great brand new and GREATER after 40-60 hrs. 

The queen has someone to break in her shoes for her..

If you are buying from a quality tube dealer they already “burned” them in before they tested them. You should be good to go. I know with my tube preamp I like to turn on for one hour before listening or if I just start listening I know after an hour they hit their sweet spot. Bottom line enjoy the music!

450 degrees for three hours.  Bast every thirty minutes.