Slow draining shower
I've dealt with this recently with two shower/tubs.
I'm going to assume that you mean a combo and just a shower because those (at least in my experience) go straight down.
For me, it was really hard to tell which way the drain went at the bottom, but it went straight back under the tub. Please don't take this to mean that yours necessarily does.
For the first one, I put a snake down and was able to get quite a bit of hair out. The snake ended up getting stuck on the way out and I deformed it some.
With the second, I just put some lye down the drain. This isn't really ideal especially if you have a septic field, but is fast and easy.