It is NOT a stupid question...How would you know , if you have never experenced it.
I have found no 2 dogs to be the same..some bleed alot more than others, they usually start with a small amount of spotting, and then it gets heavier, and they swell up and get puffy looking and sort of hard. Then the discharge slows way down, and they begin to get soft back there...and usually that is when they are ready... I stress usually, because about the time you think you have seen everything you get a surprise and your girl breeds either real early in her cycle or late. This is just me experience....My vet does AI's on a lagre scale(several a day) and they have tests to show when your bitch is ready to bred, but I have never had it done...usually my male's can tell me when she is ready !
I guess I need to add...This is my experience with my own dogs, as I have not had a female Newf in heat yet, but I have had other large breeds, and lots of small ones...and hopefuuly you will get some hints here from Newfy owners.You know, its kind of like "women" in general...when you think about it. No two of us are exactly alike, either