There is a pretty good example on https://developers.google.com/maps/documentation/javascript/examples/geocoding-simple
To shorten it up a little:
geocoder = new google.maps.Geocoder();
function codeAddress() {
//In this case it gets the address from an element on the page, but obviously you could just pass it to the method instead
var address = document.getElementById( 'address' ).value;
geocoder.geocode( { 'address' : address }, function( results, status ) {
if( status == google.maps.GeocoderStatus.OK ) {
//In this case it creates a marker, but you can get the lat and lng from the location.LatLng
map.setCenter( results[0].geometry.location );
var marker = new google.maps.Marker( {
map : map,
position: results[0].geometry.location
} );
} else {
alert( 'Geocode was not successful for the following reason: ' + status );
}
} );
}