[mslif]

If the wine is not botted at the property it was made at, it can tempered with. Most likely will be diluted or some aroma will be added to it.
You want to look for AOC (appelation d'origine controlle) meaning the name of the wine is actually from the property it was made. This is the most important thing to look for.
If you are looking for a very good wine (more expensive) you want to look for VDQS (Vin de qualitee superior) meaning Wine of higher quality. You will be able to see those letters on the bottle.
The key in french wine is not to look for the most expensive you find.

Edit; I do not want to hijack this thread either, PM me if you have any questions.