As others mentioned, there's no surefire guarantee with room requests - I feel best practice is to call and make your room requests with Member Services - I like to put in primary and secondary requests to improve my chances. My primary request often involves specific room numbers that I like - I try to provide at least 10 or so numbers - I just read them off to the agent - like 2058, 3058, 4058, 2014, 3014, 4014, and so on. Then as a secondary request, I'll put in for an area or description, like 'croquet court view, high floor near elevator, garden view rather than pool, etc.
I also then prefer to go to the desk when I arrive and do check-in there - I can see what room they have me assigned to, and request to move or try another if it's not what I was hoping for - often they'll put you in a room that's available now, but there might be a room closer to your request that isn't ready yet and I can request that, letting them know I don't mind waiting.
I've had very good luck with my room requests. I was just at Boardwalk in September, and I had requested 10 room numbers - I got one of them. In June at Saratoga, I got Congress Park, Building 1, 4th floor, facing Disney Springs as requested. February at Cabins at Fort Wilderness, I got 2800 loop, outside cabin, back of loop, with woods behind. Last December at Boardwalk garden/pool view, I got a specific room I requested on the 4th floor. The last time I didn't get my more specific request was June 2024, but I got a room 2 doors down - wasn't as good of a balcony, but the view and floor were the same...so they tried to meet my secondary request at least.
Overall I'd say I'm running about 60% success with requests. I've been on a good run the past year or so, with higher success, but still not too bad. I usually arrive for checkin between 12:45pm and 3pm (I drive up to Disney, about a 3 hour drive).