What,s the best to get bad stain,s out of old carpet

https://www.hunker.com/13404065/how-to-get-a-paint-scuff-off-wood-furniture

Rug Doctor Hire Cleaner and Machine for large DIY's.

I have some rooms with rather light colored carpets, a large dog and 3 cats, one of whom is always puking up hairballs. Nasty, and it leaves ugly brown stains. I won't even go into dog messes. My carpets are quite old and of man-made fiber. The reason I'm telling you all of this is because you might not want to try my solution on wool carpeting if that's what you have. Anyway, I've had excellent success with good old Peroxide, right out of the bottle. I thoroughly wet a paper towel and at first I blot, then once the carpet is wet (not saturated) I gently rub in a circular motion and presto! The stain is gone. This may or may not work for you, but why not give it a try in an inconspicuous area? Good luck

Resolve is a good stain remover

Call in the pros and have professionally cleaned. With all the moving activity, you will be glad you did.

First of all, what is the stain. Secondly, go to a dry cleaners, and they may give you some ideas. Or, go to a hardware store, and seek some wisdom, but know for certain, what the stain is. If you can't identify it, then many folks can't help you. J.