What’s the right approach?

Not freakin likely

Thanks guys. I do have a spotting kit and a spotting guide which suggests different spot removers for various types of things ranging from red wine to coffee and pet urine. But I think something more comprehensive in terms of a video or class would definitely help me, especially when the customer no longer remembers [or admits] what caused the spot/stain.

My main concern had to do with the billing aspects. Personally, I don't think it unreasonable to spend a few minutes, maybe 10-15 on a particularly tough spot if the room is in decent shape to begin with. But multiplying this by 3 to 5 'unknown's per room would quickly eat up a lot of time and profit.

Sounds like a pre qualification round with the customer  to inspect the carpets and set expectations is the best thing for the immediate near term, followed by some additional training/experience in spot removal techniques.

I like the ones where the carpet is so dirty you can't see the stains for the dirt.  Those are the ones you have to be really careful with the customers. 

How do you tell a customer "After I scrape some of this crud off your carpet I can tell you if I can get the stains out.

I'm just now getting back into the business (was in it in the 80's and 90's - now buying another TM/1 ton).

Anyway. I use to explain to customers that stains will not come out, most spots will. For stains I can do a cut and plug if they have additional carpet or can even take it from the corner of a closet. Some customers would take the cut and plug (up$ell)

If the carpet is absolutely filthy, I use to always write that I recommend the carpet be replaced. No Guarantees!

I read the the work order (invoice) to the customer, had them sign it to OK me to start the work, then have them sign it again to approve the work when I was completed.

Most customers KNOW when their carpet looks like S**T, others don't and need an honest professional opinion.

Just remember to always Cover Your Rear. The last thing you want to do is replace a customers carpet because you failed to note the true condition on the invoice. (CYA).