I commonly depart IFR from a non-towered airport. I can reach approach control or Center easily shortly after takeoff. My question is does ATC prefer I call them on the ground for the clearance by phone or do they prefer that i pick up my IFR clearance Airborne. Also, if it's a severe clear VFR day or does it really matter to them? Obviously if it's IFR at the airport you would always call. How severe does the weather conditions play into their preferences? There is no remote radio communication available at the airport.