Not sure if this is quite what you're asking, and it might be stuff you already do, but when relatively readless here are my "insta-read" fish-signs:

1. Posting blinds out of turn - anyone willing to pay extra to play OOP is someone I want to play pots with.

2. Weird raise sizes, ie. minraises or really big open raises.

3. Slowplaying in anything other than a really good spot for it.

4. Limping a lot obviously

5. Limp-reraising obviously

6. Sitting short, unless an obvious shortstacker with auto-topup to some short stack size.

7. Showing down wierd suited crap (other than like a BB check or whatever)

8. Calling down and folding the river where an obvious shitty draw was possible.

I'm sure there are more, which perhaps others can add to this thread. These are just the ones I can think of off the top of my head that set my alarm bells ringing and begin to build a fishy image of a player for me.