If it's possible for you to do, if the battery is the "top up type" ( Caps on the top) check that the water level is above the plates, check the - + connections are tight, check the earth to the battery is tight & clean to the body, check the connections at the starter, "BEWARE" make sure the car is in nutral before checking the starter connection, if you touch the 2 connectors at the starter solenoid, if the car is in gear it will shoot forward / reverse.