rpm,
It shouldnt be too hard to find the restrictions but it depends on the home.
how many stories,does it have a finished basement,crawlspace and the like.
Usually there's a main trunkline that supplies cold water to the various areas or leads to the hotwater tank. That would be a good place to start,at the tank,check to see what size pipe is used and if any visable reduction joints can be seen.
there's likely 1 choke point for each line,hot and cold going to the various areas.
If you've never soldered copper pipe before then do yourself a favour and hire a plumber,if you have then see if you can run new 1/2 inch pipe to the taps.
If it was me,i'd do the laundry room and main bath,possibly any onsuite and kitchen if needed. any guest or secondary bathrooms would be low priority.
If your not sure,check for a retired tradesman group and have one come and check and price the job,can save some money doing the tearout yourself.I dont mean remove pipes but any walls that may need opening,etc. Sure a plumber may do that but then your paying him big bucks!
Good luck,did my house a couple years ago,went with 3/4 and "restricted" that down to 1/2 as close to outlet as posible! great water pressure.