I always out salt on fries, never vinegar.
In Scotland, if you live on the east of the county, around Edinburgh, you traditionally have brown sauce with your chip shop chips.
If you live in the west of the country, it is fairly uncommon to put sauce on the chips from the chippie.
I always try and sneak a look at the chips before I make my decision. If they look good, then I just have salt and vinegar. If they don't look so good, I get sauce on them to hide the taste.