how to troubleshoot why starter wont turn over on 2000 Volkswagen Cabrio

car started a while ago now i press clutch and turn key over and get nothing. had my brother wiggle wires around and kicked over once now nothing. any idea where to start?

Asked by for the 2000 Volkswagen Cabrio
Test for signal voltage(battery voltage) at solenoid wire on starter , when someone turns the key to crank/start position. Connector may not be getting a good tight contact when it's plugged in.
what do i need to test it with? a test light?