AN SMT PLT SLIGHTLY DAMAGED 1 OF HIS PROP BLADES ON A TXWY LIGHT.

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I WAS CLRED INTO POS AND HOLD RWY 9L AT MIA. CONDITIONS WERE NIGHT WITH HVY RAINSHOWERS FROM NEARBY TSTMS. MIA WAS; AS USUAL; VERY BUSY. I WAS UNFAMILIAR WITH THE ARPT; BUT ON IFR FLT PLAN. IMMEDIATELY AFTER TAXIING ONTO 9L; I WAS TOLD TO TAXI ACROSS 9L (AT L2 INTXN); IN FRONT OF ACR TURBOPROP AND BEHIND AN LGT AND POS AND HOLD ON RWY 12. I TAXIED ACROSS 9L AND ONTO A RAMP AREA WHERE SEVERAL ACFT WERE HOLDING FOR RWY 9L. THERE WERE NO TAXI LINES TO FOLLOW BUT THE TWR CTLR TOLD ME TO MAKE A SLIGHT L; THEN R TURN TO GET TO RWY 12. I SAW THE RWY AND WAS ATTEMPTING TO TAXI THERE; BUT DID NOT SEE THE EDGE OF THE RAMP AND TAXIED OFF THE TARMAC WITH 1 WHEEL; WHICH MADE A THUMP AS THE STRUT BOTTOMED OUT. THE ACFT TAXIED AND RAN-UP FINE; AND I MADE AN UNEVENTFUL SHORT FLT. HOWEVER; AN INSPECTION OF THE ACFT AFTER FLT DISCLOSED A MINOR PROP STRIKE ON 1 OF 3 BLADES ON R ENG. THE PAX SITTING IN THE R FRONT SEAT WAS UNSURE WHETHER A BLUE TAXI LIGHT HAD BEEN DAMAGED/HIT. I WAS UNAWARE OF THIS. ANALYSIS: IMPROPER TAXI PROCS; ESPECIALLY ACCEPTING A TAXI CLRNC UNDER ADVERSE CONDITIONS (NIGHT; UNFAMILIAR HIGH DENSITY ARPT; RAIN; BAD WX) WITHOUT KNOWING EXACTLY WHERE TO GO BEFOREHAND. I HAD AN ARPT DIAGRAM ABOARD AND SHOULD HAVE USED IT. I ALSO COULD HAVE CLRED 9L AND THEN HELD POS BEFORE PROCEEDING BTWN ACFT TO TRY AND GET IMMEDIATELY TO 12. IMPROPER NIGHT TAXI PROCS; FAILURE TO SEE AND RECOGNIZE TXWY EDGE. PERCEIVED PRESSURE OF HOLDING UP OPS AT BUSY ARPT INCREASING 'URGENCY' OF IMMEDIATELY ACCEPTING ANOTHER 'POS AND HOLD' CLRNC AS WELL AS PROBABLY TAXIING TOO FAST. IMPROPER CREW COORD: R SEAT PAX WAS PLT (LOW TIME) BUT SHOULD HAVE BEEN INSTRUCTED BY ME TO HELP LOCATE TXWYS; ACFT; RWYS; ETC. TALKING TO HIM LATER; HE DIDN'T WANT TO VOLUNTEER INFO HE THOUGHT I ALREADY KNEW OR DISTURB ME. HE SHOULD HAVE BEEN MADE TO FEEL HIS CONTRIBUTIONS WOULD BE APPRECIATED BY THE PLT (ME). DECISION TO TKOF -- I DIDN'T KNOW THAT I HAD DAMAGED THE ACFT PRIOR TO TKOF; HOWEVER; I SHOULD HAVE IMMEDIATELY TAXIED BACK TO PARKING FOR THOROUGH INSPECTION PRIOR TO TKOF AS SOON AS SOMETHING UNUSUAL HAPPENED. I WAS CAUGHT IN THE 'FLOW OF GOING' AND DIDN'T STOP TO ADEQUATELY CONSIDER ALL THE POSSIBILITIES.