C421 PLT HAD A RWY INCURSION ON RWY 12R AT HOU.

Narrative

I WAS TAXIING N ON TXWY G FOR TKOF FROM HOUSTON HOBBY'S RWY 12R. I WAS SLIGHTLY DISTR BY MY CONVERSATION WITH GND CTL AS TO IF AND FOR HOW LONG; I WOULD NEED FOR ENG RUN-UP. A SUBSEQUENT FREQ CHANGE TO TWR FREQ TOOK MY SCAN INSIDE THE COCKPIT AT THE CRITICAL TIME AND I FAILED TO OBSERVE THE HOLD SHORT LINE OF THE ACTIVE RWY 12R. AS SOON AS I LOOKED UP; I STOPPED THE ACFT EVEN AS TWR TOLD ME TO STOP. A B737 WAS LNDG AND WAS ABOUT 1/4 MI OUT AS I STOPPED. THE B737 CONTINUED HIS APCH AND MADE A NORMAL LNDG. ALTHOUGH I WAS NOT ON THE ACTIVE RWY; I HAD DEFINITELY CROSSED THE HOLD SHORT LINE. A LACK OF FAMILIARITY WITH THE ARPT WAS A CAUSAL FACTOR; IS (I HAD THE BIG ARPT DIAGRAM ON MY LAP) BUT THIS; CERTAINLY NO EXCUSE. ALLOWING MYSELF TO LOSE SITUATIONAL AWARENESS WAS THE PRIMARY CAUSE OF THE RWY INCURSION. OBVIOUSLY A STRICTER ADHERENCE TO WHERE THE ACFT WAS ROLLING WOULD HAVE PREVENTED THE INCIDENT. THE TWR'S TIMELY INSTRUCTIONS WERE PROFESSIONAL AND EXACT. THEY WERE ON TOP OF THEIR GAME -- I WAS NOT ON TOP OF MINE. PRESETTING TWR FREQ IN THE RADIO AND SOLICITING INPUT FROM THE HIGHLY EXPERIENCED PAX IN THE SEAT BESIDE ME TO 'LET ME KNOW IF YOU SEE SOMETHING YOU THINK IS NOT RIGHT;' IE; PRACTICING GOOD CRM; COULD HAVE AVOIDED THIS INCIDENT.