Crobat can only be obtained by making a Golbat evolve by happiness. That's it. A detailed explanation on how to make it happy is in the READ FIRST
thread as well as information on feebas. Please read this thread first to see if your answer is in there before asking questions.
As for the others...
Spoink-jagged pass (some)
Staryu-lillycove city (some-super rod)
Chimecho-Mt. Pyre (very top) (few)
Pinser-Safari Zone (Northwest-need mach bike) (few)
Heracross-Safari Zone (Northeast-need acro bike) (few)
Snorunt-Shoal Cave (lowest floor-covered with ice-when the tide is out) (some)
Dragon Scales can be obtained by using theif or covet on some wild bagon and horsea. Keep in mind that few of them even have one attached so it'll take a little while unless you're lucky...