Eating a low cab diet essentially means that you'll be replacing (most of) the energy that you were previously getting from carbs with energy from both dietary and stored fat sources. You need to go fairly low carb to force your body into making this switch.
I'm another who just cut out the obvious culprits, but did it in 2 stages because i was initially advised to avoid sugary food, so cut out sweets, cake, biscuits, jams and sugar itself. A little research told me that all high carb foods were what I should actually be avoiding so then added potatoes,bread, cereals, rice, pasta, etc to my Do Not Eat list. I didn't have a meter until after I found our forum, but by simply cutting out those foods I reduced my HbA1c from just over 60 at diagnosis, to 47 - so just about prediabetic - within three months. Getting my meter and doing some fine adjustments has shown me that I can manage to keep my levels down to bottom end of prediabetic by aiming to eat no more than 50g carbs a day, and still enjoy a wide range of low carb food, and this I've done for over 4 and a half years now.
Since we're all different, we need to find our own levels at which we can keep our glucose both as low as we can and stable, and at the same time eat a diet that's sustainable long term.
Robbity