Just been diagnosed and prescribed 850mg metformin twice daily. No other info from doc about what I an supposed to do now. Only told to come back in two months.
So it's not just France that leaves their diabetics to fend for themselves!
Rule 1 - has already been said. Get a log aka a Notebook - record Blood Glucose readings in the morning, and one and/or two hours after meals. You'll use a lot of test strips to start with but it's a good long term investment.
Cut back or eliminate sugar (and artificial sweeteners) and high carb items such as bread, pasta, rice potatoes. Track your meals so you know which foods cause you to spike after meals. Don't waste your time with products marketed "specially for diabetics" - they are all high carb and full of artifical ingredients that will do you no good.
Track your weight - I log mine once a week. That way you'll see as you cut your carbs how the weight drops off!

(I lost 28 lbs in six months)
Blood Sugar 101 is an absolute gold mine of information - and the book ain't bad either.
Ask this forum for ideas - there's lots of us out here and we all have the same challenge - it's called diabetes. It's not a nice condition but it can be managed as long as you are prepared to discipline yourself to follow your own rules.
It's also a condition that is very individual - whilst there's lots of basic ground rules that apply to us all, some details that work, for instance, with me may be a complete waste of time for you - and vice versa.
Welcome to the club.
John