try it in different steps... that's what I do with Arduino coding... I do one piece at a time then put it all together.
So for your project, which I'm doing the same exact thing, but not right now... I'm working on the GUI first.
Anyway, I would approach it like this:
Use a switch (momentary) to one of the pin, then when the switch is pushed, set the door solenoid to lock / unlock depend on the kind you got.
This will test to make sure your door strike circuitry is good and that it's working.
Then, write a code for the Parallax reader... when it read correctly, turn LED green, else keep it red.
This will test the reader...
Then put it all together.
I have it all working already... but my circuitry is different since I use a variable voltage regulator to feed 5V power into the Arduino instead of straight 12V... then I used a MOSFET to power the solenoid instead of a transistor.
You can see my video here:
No RFID reader on that yet... I'm using those in a different design right now, so I haven't add it in yet. We're doing the same project on this post:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1278347111/120#120