How to Torque up bolts correctly?

I'm probably going to look like a complete numpty asking this question, but what is the correct way to check you are torquing up bolts correctly?

Normally I would just set the torque setting on the wrench and just tighten until it clicks. But what if the bolt/nut has been over tightened in the past? Is it best practice to loosen it off first then tighten back up to the desired torque? Is this the 'normal' way of checking things like subframe bolts?

I wouldn't bother loosening them first.

The subframe bolts are unlikely to be too tight , just tighten them to the correct torque. They aren't that critical like some other parts on the car.

With other things just tighten them to the correct torque if you are putting them back together or if you are checking their tightness.

Just a hint, why not use a Nordlock Washer on the sub frame bolts. That way when you torque them up, they will never vibrate loose.

Railway Technology eh?

They look like a good thing actually Tony. Never heard of those before.

Used to use them on MRI machines. The serrations mean that you have to increase the clamping force (increased torque) to undo them. As it's impossible for a vibration to do this, they can never come undone. Shouldn't imagine they'll be expensive either.