Pretty straightforward. I always do it before. Which, if either, is better, and why?
My dentist always says floss first, then brushing cleans out the debris left by flossing. Have never heard an argument to the contrary.
Here’s a previous thread on the same topic. For what it’s worth, I usually follow the same routine as CookingWithGas for the reason cited, but occasionally I switch it up when I want to use the same stream of hot water from the faucet to rinse both my hands and the toothbrush bristles.
Huh, I always floss after because that’s how my dental hygenist does it. When I go in for a cleaning the order goes:
Scrape plaque with pointy metal things
Brush with special toothbrush
Floss
Why do they do it in the wrong order at the dentist? Or does your dentist floss first?
I feel like if I flossed first I would get tons of food out whereas flossing after just gets the little that’s left. Brushing gets most of it out and flossing is the finish work.
Hmm, looks like we have two schools of thought here with a great deal of reason on both sides. Perhaps some sort of battle royale/Dentist Deathmatch is in order?
I believe most dentists recommend brush first, then floss.
The hygienist may do it differently because the cleaning procedure has different goals from brushing/flossing after a meal. Presumably one doesn’t go in for a cleaning unbrushed.
I like to first brush once over lightly with no toothpaste, then floss, then brush with toothpaste. Rinse before and after and between steps.
That was going to be my answer as well. But I just went to the dentist with an emergency twice in as many days. And I’m now looking at a lifetime of eating applesauce and pudding. So you might not want to take my advice on dental care.
If you don’t follow the dentist and don’t floss second, you’re an anti-dentite!
A raaaaaaaaaabid anti-dentite!
FWIW, I always get complimented on my oral hygiene when I visit the dentist, and I floss first. In fact, the last time I went I hadn’t been for over two years and they couldn’t believe how clean those bastards were.
A possible theory could be that the toothpaste works best when a small amount is left on the teeth. Flossing would rub the residual toothpaste away. Just a wild hypothesis.
Come on, I have a life to live! 
My dental hygenist just emphasized that one should floss first, then brush to remove all the debris loosened by the floss.