How do I sync my Google calendar with my iPhone?
So I want to be able to add appointments/events/tasks on either and have those changes reflected on both.
You should really use Google Sync for iPhone to have all the benefits of Calendars (and even Mail if you need it).
In iCal, add a new CalDAV account.
Server Address: www.google.com
Server Path: /firstname.lastname@example.org/user/
Use SSL: CHecked
Make sure you have sync enabled in iTunes.