Make sure all your connections are clean (battery solenoid and starter) If you turned the key and had nothing then the solenoid did not activate. if you had a solid click then it engaged. if it had a weak continuous clicking (growling) sound it could be dirty connections. if you have no sound at all when you turn the key check for voltage at the solenoid pin with the key in start position.(the small ipins on the solenoid) it should be the pin on the starter side of the solenoid unless you only have one pin then it's that one. If you have voltage at the pin and your battery is good and all the connections are clean and tight and the solenoid is not engaging then I would go for the solenoid.
if it is engaging check for voltage at the starter if you have voltage at the starter and it is not working  I would replace the starter You also want to make sure your ground wire is connected to the chassis and the engine
Good luck
Joe

After some delay in dealing with this... I was able to fix the problem...  and now my Pinto drives again! 

I put in a newer battery, and the starter still wouldn't turn over.  Also had some small flames on the side of the starter near the positive cable -- the arcing had ignited oil that was on the starter, from oil leaking from the valve cover, and possibly the oil pan gasket -- the oil had coated the positive connector on the starter, interfering with the electrical connection.

I disconnected the battery, jacked the car up and removed the positive cable from the starter, as well as the connector strip.  I then sprayed the connector with carb cleaner, wiping it super clean, and reconnected it.

Reconnected the battery, and she turned over.  poured a little gas down the carb (she'd been sitting for a couple years or more) and she started up.

Now I have to learn to get rid of the oil leaks.  But at least she runs.