Your starting point is Trust No One.
Over time, you'll begin to get a sense of who and which places and brands are likely to actually be aware of what gluten free means - but in that process, you'll have plenty of 'There's no meat in it' (but lots of wheat), 'Can't you just eat a bit less if you want to lose weight?' and assumptions that you'll be fine picking around the wheat containing products.
Never trust a buffet unless you're literally opening the packet - that GF dip would have been great were it not for the person before you who stuck a breadstick in it and cheese was fine until it was cut with the knife that was used to open a bread roll, as was the antipasti until somebody thought it would be nice to artistically arrange it on a platter with crackers, breadsticks, mini sausage rolls -and all of the fruit and olives you now can't eat, either.
Italian restaurants are generally very good at understanding GF and South Indian ones can be very helpful due to the amount of foods that are inherently GF and made from fermented rice flour instead.
You'll also get used to which shops actually stock gluten free options beyond snack bars and cake - out of seven supermarkets in a three mile radius where I live, I have found one single GF sandwich on one occasion and on that same occasion, three GF frozen items.
GF will always be pushed out in favour of seasonal promotions - you can write off the entire Christmas period because if you find a store that actually sells more than a couple of snack bars and some cakes, everything will be swept off the shelves come November in favour of more party food. And if you place an order for a Christmas delivery, treat it as a child writing a list for Santa, as it's pretty much guaranteed that the GF panettone, Christmas cake, mincemeat and other products that weren't already marked Out of Stock on the day you placed your order will fail to arrive in much the same way as your Mr Frosty and a Pony never turned up on Christmas Day despite your carefully adding them to your list every year without fail.
If you sign up to Food Agency alerts, you'll get a message about six weeks later to tell you when a specifically gluten free product has been found to contain undeclared gluten. But you'll know all about it by then, it just confirms what you've experienced after eating.
Be aware that you may also have to avoid all oats, including gluten free ones, as it's possible that Avenin is an issue for you - and it's very common for the damage already done by gluten to cause lactose intolerance. Unfortunately, this eliminates the majority of dairy free alternatives, such as ice cream, as they normally contain gluten and/or oats.
If you cook from scratch at all times, take your own food and always plan for not being able to eat because your promised GF option has been cross contaminated or somebody else has taken a fancy to it, it's much simpler than to try to navigate all the preprepared options available at first - and the longer you go without something you've eaten all your life until diagnosis, the better an alternative tastes.