What is your "golden" advice to the newly diagnosed?

Get a blood glucose meter and lots of strips (SD Codefree is the cheapest)
Use it.
Map out which foods cause your blood glucose to rise too much.
Reduce or eliminate those foods

And you will have your own, tailor made diet for your unique body, that will allow you to control your blood glucose, your future health, and probably your weight.

agree with @Brunneria
knowledge is power -- and knowing your BG level is paramount in shaping your D future

Take anything you are told, that you don't understand, as a signal to do more learning.

Control your diabetes and high blood pressure i was warned about future problems in my late teens.now 30 yrs ltr am on dialysis 3 times a week

As already suggested:
Be aware that carbs both in the form of sugary and starchy foods are your enemy (in spite of what your diabetic team may tell you to the contrary!) - as they raise your glucose levels, so avoid them where possible! Get a meter to check your body's reactions to various higher carb foods (and also to stress, pain, illness), learn and adjust your diet accordingly. And definitely do your homework and ask us here if you don't understand something.

Robbity

Get a meter and test every new food until you are comfortable you know how your BG will react.

At the start, I tested before my first bite, at one hour from first bite, at 2 hours from first bite, and (if hour 2 was higher than hour 1) at 3 hours. I tested everything new at least twice - and if I was still getting inconsistent responses, I tested some more.

Weight loss is generally not a bad idea, but using your meter to guide what you eat is typically a much quicker way to make a dramatic difference in blood glucose. It may also make a dramatic difference in the way you feel. I did not realize my high blood glucose was making me fatigued and foggy brained; I just thought it was due to being overworked. Until I got my BG under control. Even though I am just on the other side of completing cancer treatment, I still feel at least 100% better than I did at this time last year - about 2 weeks before my diabetes diagnosis.

LOW CARB
FULL FAT
EAT TO YOUR METER
RESEARCH
ASK QUESTIONS ON THE FORUM
LISTEN TO THE ANSWERS

Test test test !!!
CAROL

Stop eating Carbohydrates.

DO:
Test
Experiment
Try new foods
Find an exercise you enjoy
Ask loads of questions
Laugh
Spend lots of time on this website
Look after your feet

DON'T
Let the medical profession bully you into something you're unsure about.
Get too despondent - get on the forums
Think it's your fault you got diabetes in the first place.

As a prediabetic, reduce your carbs, reduce your plate size, increase your exercise.
Test, record, test, record.
Knowledge is the key to unlock your future health.

Never get complacent and think you are cured once your HbA1c drops to non-diabetic levels.
Carb creep is all to easy if you relax and stop testing.
This is a life-long challenge.