There is a schedule of departures and pick up times on the Southern California Gray Lines website. It tells you what time you will be picked up from your hotel and what time you will be at the airport.(
http://graylineanaheim.com/docs/GL Anaheim DRE Brochure 2009.pdf) Therefore you choose when you need to be at the airport, check the corresponding hotel pickup time and be at the pick up spot to catch the bus. When we went in November we didn't have a problem at all with the service. I booked a round trip online and printed off 2 vouchers. One for airport to hotel and the other for hotel to airport. When I booked it the email told me to call and confirm what time I would be using the service when I flew into LAX and they told me to call 48hrs prior to my departure day to ensure that the bus stopped at my hotel - I think they like to have a preliminary number of people. When I boarded the bus each time, they took my printed voucher and it was done. I know that people who are taking the DLE to SNA got picked up by our bus at their hotel and then had to change busses at the DLH. I thought the service was affordable and reliable. I will be using them again in July and will be coming from SNA rather than LAX. There is also a $5off coupon on the orange county website.