The subject comes up a lot. I'm going to share what I have done and explain as best I can but I do know that this is probably not the best for many or those who want more accuracy. As the saying goes, it works for me.
I own several bar type torque wrenches. They all happen to be Sturtevant before the name of Richmond was added. I use them to check my clicker wrenches every time I use a torque wrench.
The bar wrenches are accurate and the clickers are used for repeatability. I have bought all of my clickers on eBay at the cheapest prices. I buy Name Brand wrenches. maybe you don't know what they are? Snap On, Matco, Utica, Bonney, many others.
I own the correct wrench for what I am working on. !/4, 3/8 or 1/2. I have low end torque wrenches in 1/4. medium range wrenches in 3/8 and higher end in 1/2. I do not need anything above 250 ft/lbs so I don't need that monster used on Mercedes Benze. But if I did I mifght be tempted to use math instead of an expensive wrench. (if it was a one time thing)
Use a wrench that has the torque you want in the middle of it's range, never the lower 10% or highest 15% of it's range.
Clickers are made with a spring inside that is stretched as the torque is raised. NEVER leave a clicker set at higher than 0 when stored. But if you do then check it, it wil probably be OK if not too long (years) or too high.
Exercise the wrench before using. When checking that it is reading the torque you want with the bar wrench move the wrench to left and right and upper and lower settings. Final check?
Something I saw posted once from somebody that claimed to be an expert and was taught him by a pro too many years ago was that after using the center out pattern and the cross pattern and the every other nut pattern and stepped increases bolt patterns was, make a final pass at final torque in a circle of all fasteners. I've only seen this mentioned once and it make a bit of sense but I don't see it as necessary. Any thoughts?
Just an old guys thoughts. I'm not a pro and if I was I think I would know more about this subject.