Why does your new starter just click?

1. Battery is weak
2. Battery posts are dirty and not allowing good connection
3. Wires are not in good condition
4. Bad ground to engine from battery
5. Wire not tight on starter
6. Solenoid is defective (on fords and other cars with separate solenoids)
7. Defective starter (even new ones can be. I bought a bad one in Sept.)