I break it into quarters first 12-3, 3-6, 6-9, 9-12. I break it into thirds next, this gets the hour.

Then for minutes i do the same and just do quick caculations in my head,

1/3 of a quarter before 6 is 25 minutes, 1/3 of a quarter after 9 is 50 minutes.

The only thing im really remembering is that values at the quarters,

(12/0 hours - 0 min), 3 hr - 15 min, (6 hr - 30 min), 9 hr - 45 minutes.

After a while it becomes second nature. I learned this when i was a kid because digital clocks werent as common then.