Step 1: The Schematic Diagram
The electrode connected to the secondary is not heating.
Increase the value of C3.
The electrode connected to the transistor is not heating.
Decrease the value of R3. If this does not fix the problem replace Q3.
Little or no output and lots of heat, drawing lots of current.
Decrease the value of C2 and shorten air gap in core (transformer covered in next step), check feedback winding polarity. If this does not fix the problem replace Q1 and Q2.
Lamp fails to strike at 12v input, ends glowing brightly.
Decrease the value of C4.