The biggest challenge is no moisture, use flux, heat one side, apply solder to the other, repeat. Run the flux brush around the solder joint, wipe with a damp rag, cool everything down with a spray bottle of water.

For a DIY'er... 1word...SharkBite! Solder joint for dummies ( not that you are a dummie John )

I use shark bite stops for temporary stops. They are not allowed in all locations. I don't like the fact that if you connect elbows or shut offs that you can turn each piece, and actually spin the shutoffs.

Norm brings up valid points regarding the SharkBites. What exactly are you soldering John?

Soldering is best left to a plumber with the proper insurance.

Falling back to code...pressure testing of plumbing pipes is mandatory. We install a pressure gauge on the water lines that has a standard air intake for a tire chuck. Available at a local plumbing supply, you use compressed air to pump the system up to 100 psi. That needs to hold for 24 hours at a minimum. Leaks hiss! But since it is air, not water, re-soldering is a lot easier. If you are doing a remodel, locating a ball valve on the existing lines isolates the new work and minimizes the problem of a bad joint full of water.

Oh yeah! Don't bury that ball valve in the wall or ceiling! It needs to be accessible!