Need Tips on Measuring for Replacement Windows

I’m looking to replace the windows in my home and could use some advice on how to measure for replacement windows accurately. I’ve done a bit of research, but I'm still feeling a bit unsure. Do you measure from the inside or the outside? And what about accounting for any trim or framing?

Also, any tips on tools or techniques to get the most precise measurements would be super helpful. I want to make sure I get it right the first time to avoid any costly mistakes. Appreciate any help or pointers you can share. TIA!