Part II,
The Controller's Handbook, 7110.65 basically says we can issue an IFR clearance as soon as we have enough information to provide proper service. If you are already in my terminal airspace, and simply want an IFR clearance to descend into one of the airports in my facility's airspace, I really only need your callsign, type, and what approach you want to fly. I can then formulate a clearance and issue an IFR beacon code, (that is, a transponder code that will provide Minimum Safe Altitude Warning or MSAW), get you to the IAF, make sure you have the appropriate WX info. I can do this all without entering any info what-so-ever into the NAS. The computer entry in my ARTS would look like:
N12345
C172
^GTU
+ (for MSAW)
(enter)
No strip will be generated, I can hand write one if I care/need to. An IFR code from my facility's local code bank will display, and that's it.
If you're asking for an IFR clearance to a place NOT in my airspace, I'll probably have to enter that clearance into the NAS. The info I will need to enter is:
AC ID, Type, Equp, TAS, ETD, Alt, and route; in that order. For example, you call me north of AUS wanting to get an IFR clearance to Stinson Field, south of San Antonio, and you're in a Skyhawk, I'll get the fellow at the FDIO terminal (Flight Data position) to type:
FP N12345 C172/A 110 P1605 60 CWK..SSF (enter)
Note that there is no provision what-so-ever for Fuel, SOBs, color, alternate, etc. Controllers only deal with clearances. The NAS computer will generate a strip, assign a NAS IFR beacon code, and a Preferential routing if necessary. It will also generate a strip for SAT approach control, and allow me to make an automated handoff to SAT approach.
Generally, I can provide service for short-range IFR clearances any time I'm not down the tubes busy. It might take a few minutes, so I don't recommend departing VFR with an 800' ceiling expecting to get an IFR climb right away under any circumstances.
Now, If you, for some reason, want or need to air file a full flight plan for a 600 mile flight, I'll probably tell you to call AFSS. I'm not inclined to have you tie up my frequency for 90 seconds reading a full flight plan to me over the air when I don't have any use for half the info anyway, and I don't have any way to record the info anyway, other than on the voice tapes.
Hope that helps you understand the process and considerations. It's lots easier to get a pop-up IFR clearance from the controler if you're going to stay in his/her facility's airspace. If you want to file a full FLIGHT PLAN, call AFSS.