Replace hot supply line

Gas WH currently has 1/2" hot supply line. Cold supply is 3/4".
I want to replace 1/2" with 3/4".

Can you add anything (or correct) the steps I need to take:

1) shut off water from main or valve going to WH
2) turn off gas going into WH
3) empty hot water by turning on lowest fixture in home
4) do I also need to drain the WH with a hose running to a floor drain?
5) solder new copper pipe w/ 3/4"...and also add a heat trap.
6) turn everything back on and check for leaks

I install a union fitting on both hot and cold lines. Also dont forget to use the proper transition between different metals. There are different methods do do this some examples are; dielectric unions, dielectric nipples, brass nipple or stainless steel nipple.

I think I will leave the unions alone, although they do look pretty corroded.

Is there anything else I should do other than replacing the female adapter from the nipple (shown in the image) and soldering new 3/4" pipe?

You should be ready to go. However I would first pre fab the female adapter into a small piece of pipe, let it cool and then install it. Also use teflon tape and pipe dope on the threads.

Good call. Thanks!