Do I use glossy paint on the walls and flat on the ceiling?

That depends on the look you like.

depends on which room you are painting - personally, for walls I never use glossy paint - I either an eggshell or a matte finish, (some like a satin finish) - glossy is typically reserved for the trim work

I used glossy paint on my ceiling for added light reflection and satin finish on my walls. Satin finishes clean easier than flat.

definitely flat/eggshell on the ceiling. I would avoid gloss on the walls, only because EVERY imperfection will be highlighted. I also prefer eggshell on the walls, because it just gives a softer feel.

The traditional rule is...Glossy paint where you need to scrub like a kitchen / bath. Flat paint in a formal living / formal dining room. Gloss on the wood work all over.

I painted our walls glossy because my husband was constantly getting dirty marks on them that were hard to clean off. As a surprise, he painted the ceilings for me, you guessed it, with the glossy paint. However, I’ve found that the reflected light brightens up our typically dark hallway and livingroom. It does show the flaws on the walls but it also cleans really well. So basically, it’s a matter of what you like.