At a minimum, 1st thing in morn, saliva and urine PH. Usually between meals and last time to bathroom before bed also. Additional if symptoms related to acidosis develop.
Others may not have to watch as closely. For now, unusual PH is my best early warning to up the drink. baths, and take other preventative measures. Also to analyse and see if I can figure out if one or more of my food sources is not of sufficient quality. I have been so sick for so long that I need to be really careful.
I am slowly learning which patterns mean that I am doing well, and which indicate trouble. One of the trickiest occurred when I had severe chemical exposures a while back. Immediately afterward, both saliva and urine tested very alkiline. I did not realize that I was dumping my reserves in response to the toxic stress, so did not up detox baths or the drink. Had a bad spell, but leaarned something!!!
Am realizing that a refractometer is a must, just as ML says. Going to look into one.
Hope this might be of help!