The codes are helpful, but they don't cover a lot of the basic problems.
My usual check list is to check for spark on each cylinder, which is easiest
for me - by hooking up a timing light and clamping the pick up to each
spark plug wire. Then check the injectors to see if each is working -
they sell a cheap plug in light module at most auto places, or you can listen
to each with a stethoscope. Make sure you have compression on the compression stroke, either screw in
a compression gauge - or just put your finger over the spark plug hole and
make sure its blowing every other rev. Screw in a compression gauge
to the ********* in your intake to see if you have adequate fuel pressure(be careful since there already should be residual compression- go by the manual
instructions) Look under your hood in the dark as someone cranks the motor,
usually you can pick up mis-fires or arcing electrical problem.
Good luck
