Generally you are brought to the station and processed. Processing can take a number of hours depending on the facility and a number of other factors. Once you are processed then most places have your bail amount posted and allow you to make a call.
It truly depends on the circumstances of the arrest. Sometimes the person is taken into custody and, in North County, taken to the Vista Detention Facility (VDF). At VDF, depending on the crime alleged and the person arrested, the person could be held upto three work days for their arraignment unless they bail out. In other cases, the person may be booked and released with instructions to report to court on a particular day. In some minor cases, the person won't even be brought to VDF, but simply issued a ticket instructing them to report to court at a future date. In some other cases, the police don't arrest the person, but the District Attorney's Office later sends the person a notify letter instructing them to report to court on a particular day. If you think you're liable to be arrested then it's a good idea to be proactive and contact a local defense attorney now to see what can be done to ensure things do not get any further out of hand. Good luck.