If I'm on a VFR flight plan and radar identified with a unique squawk, and get handed from one center to another or from center to approach do I have to check in with the new agency with all of my information or just my callsign?
I used to know, but I haven't flown anywhere but A-292 for a looong time.
Just call them up with your altitude. Your information is passed from controller to controller as you're handed off.
Approach to center, center to center, altitude and C/S is fine. Center to approach, make sure you have ATIS and intentions as well. Approach to tower, position and intentions
What these guys said. And secondly, I'd defer to the jet guy because they are used to talking on that radio thing...
But seriously... Approach to approach, Approach to Center, altitude and callsign is fine. Center to Approach, and specifically when being handed off to the approach controller handling the airspace to your destination, get ATIS first.
So for example
Socal Appch: Navy 7G735, contact LA Center 1XX.XX
You: Roger, 7G735 switching.
You: LA Center, Navy 7G735, level 5 thousand.
LA Center: Roger Navy 7G735. Radar contact. Altimeter 29.92
Second scenario. You're landing at Palm Springs.
LA Center: Navy 7G735, contact socal Approach, 1XX.XX.
You: Roger, 7G735 switching.
Then you roll ATIS for Palm Springs, followed by the switch to socal.
You: Socal Approach, Navy 7G735, level 5 thousand, palm springs information foxtrot, with request.
Socal: Roger Navy 7G735, say request.
You: Navy 7G735 requesting Vectors to final for the GPS 31L.
Socal: Roger, Navy 7G735, you can expect that. Palm Springs altimeter 29.92.
Even when rolling through an approach frequency in-route to destination beyond, it's prudent to get ATIS (if there's one big airport in that airspace) for SA. If you don't get it, you may or may not be asked if you have it, but better safe than sorry.
Really the only time you'd have to regurgitate all the info like position, altitude, ATIS information etc is if you hear "Radar services terminatied, squawk VFR, frequency changed approved" and you contact a different controlling agency later on, but that is sort of obvious.
IFR procedures are very similar (as in the second example: requesting an approach).