One way to find out: get a bunch of friends to push it to the top of the hill, get in, get 'er rolling in second gear with your foot on the clutch, and once it picks up a little speed, ease off the clutch and the engine will catch. A bit of driving and the battery should get back into order, unless it actually needs replacing.
Oh, wait, though, I don't know the automatic-car version of this…
If it's not the battery, the second most common thing is plugs 'n' points, which aren't a dear thing to fix.