Tap the solenoid, if it goes after that then plan on taking the solenoid off and repairing it, its probly a 10 minute fix and if need be will only cost $10 bucks to repair aswell. 
I believe it's the solenoid that is clicking
I believe it's the solenoid that is clicking
If you can reach the solenoid.. try tapping it with a small hammer while someone tries to start it...
The big copper washer inside the solenoid may have a burned spot on it...
Replace the battery....
If it has a dead cell... it will never charge, no matter WHAT kind of charger you have and it may nut even start if you try to jump it off.