I seem to have a knack for picking what looks good on me. It seems foreign to me NOT to know how to dress. I guess it's a skill like everything else. If you don't know, or are unsure, asking is the best way to find out.
I've always been into fashion though. For jeans or pants, I absolutely MUST have a mid or high rise or I have that tire around my middle (I'm an apple shape). Leg style doesn't matter because I have long legs - 33" inseam - and have rather shapely legs even for my size. I look better with slightly longer length shirts, with a flowing or empire design (or straight fit) and I almost always go for a 3/4 length sleeve over short and something with an open/lower neck. I have good cleavage so I show it off. Tanks layered under blouses, jackets, hoodies, or cardigans are also a staple for me.
I never choose hip huggers, shorts shorter than bermuda length, nothing with a sheer or open back (rolls are a problem), peplum shirts (though I love them) or shirts with a drawstring or belted waist (unless I control the location of the belt, wearing it higher). This is because it hits me right in the middle of my belly roll and look TERRIBLE. I also don't do pencil skirts because my 'bumpy' front, even in spanks, which I wear fairly consistently.
Last, I wear heels almost all the time - boots, shoes or sandals even though I'm almost 5'10". I don't care, I'm an amazon in them, they make me feel good. Even when my knee is hurting, I suck it up.
I shop thrift, new online, outlet, and belong to a couple local plus-sized clothing groups on Facebook. It helps fill in my wardrobe as I'm dropping weight without breaking my wallet.