One way I thought was interesting was to use the knuckles on a hand and the dips between the knuckles.
All the knuckles from left to right are months with 31 days, the dips are either 30 or February. When you get to the far right knuckle, tap it again and go backwards. This is what gets you July and August with 31 back-to-back.
That said, I do prefer the rhyme "30 days hath September, April, May and November. All the rest have 31, except February which is all f-ed up!" 😁