KSNA is my home airport. Feel free to give me a call if you want some quick tips. I'm on PDTime. 949-285-6582
http://www.pilotsofamerica.com/forum/#
On arrival, make sure you are on flight following. So Cal approach will help you along. Just make sure you know where the LAX class bravo is. LAX class bravo is the mother of all mistakes. They take it very seriously.
Departure is easy so long as you are not heading through Class B. Sounds like you will be so be ready. The minute you transfer from SNA tower to So cal departure they will ask you how you plan on navigating LA Class B airspace. You will need to get a clearance prior to taxi with clearance delivery. I generally tell them in advance which route I intend to take getting through Class B. Maybe overkill but I think they pass it along to So Cal. DO NOT ENTER CLASS B until you hear the words "you are cleared into CLASS B airspace". Don't assume anything until you have heard those words. If you don't hear them, ask! The controllers that work the LAX class B airspace mean business. They are really by the book.
Be familiar with the approved transition routes. Some of them require that you get to an altitude (can't recall how high exactly) that is very difficult to get to in a short period of time. Especially if you are in a small 172ish airplane. There is a lower route so you might want that one. Buy the paper Chart for the Class B transition. Don't rely on foreflight.
I have done the LAX transition a bunch, and still get nervous. If your prepared it will go easy. If you go out on an instrument flight plan you won't have to worry about any of this. I fly a bunch but my route of flight is generally the opposite direction of LAX.
The LA basin is the most intimidating I have encountered. (never been to Boston or NY)
Gas at SNA is $8 per gallon plus. Tie downs are expensive too. I'm gone many weekends so if you are coming a weekend that I am away, you are welcome to my spot.
Good luck. And welcome!
Andy