Winter is a actually fine time to get started! In fact, you might consider getting your technique up to speed on a stovetop griddle or skillet, where you don’t have to worry about the flare-ups and highly variable temperatures of a charcoal grill.
Assuming you’re not grinding your own beef, get 80% ground chuck from your grocery’s butcher counter. Avoid the store-brand 2 lb tubes of ground beef, because who the hell knows what’s in it. They are cheaper—for a number of reasons, and none of them are good.
Start with chilled meat (you don’t want the fat smearing everywhere), and go gently while you’re forming the patties. I mix in sauteed chopped onions, cocking a snook at Kenji Lopez-Alt, but the general rule is to leave the beef unadulterated, except for adding some salt and pepper just before cooking.
This. As it cooks, the patty will shrink from the sides and rise in the center, which is where the “divot” instruction really helps. I’d also recommend you resist the temptation to go too thick. You want your patties flatter, rather than taller. Thick burgers do have the advantage of not drying out as much, but OTOH they’re harder to judge when it comes to doneness. Definitely explore thicker burgers later if that’s your thing, but to start with I’d concentrate on getting a good sear with a fast cook.
Get a hot, lightly greased surface going. Slap the burgers on and leave them severely alone (another cock-snook at Kenji Lopez-Alt, who thinks you should continually monkey with them. Maybe when you’re as accomplished as he is you can, but beginners, and I still include myself here, should stick to letting the burgers do their thing).
Then when the burgers “release” from the grill/pan and become easy to lift, turn them. Cook awhile longer, until you see juices bubbling up through. They’re probably done now. Preferences vary wildly, but I like my burgers cooked to the high side of medium, especially with store-bought ground beef.
Finally, I’d stick with simple sesame seed hamburger buns, rather than giant fancy buns. The bun is just a handle; the point of the hamburger is the burger and its condiments, not the bread.