A DEHAVILLAND DASH 8 FLC DID NOT FOLLOW A LONG AND COMPLEX CLRNC ON TAXI OUT OF LGA.

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WE WERE INFORMED BY GND THERE WAS A HOLD ON TFC OVER ELIOT INTXN FOR OUR LGA-IAD FLT; IT WOULD BE ABOUT 12-15 MINS; SO THE GND CTLR HAD IT IN MIND TO PUT US IN AN UNCONGESTED TXWY AT LGA. WE THOUGHT SHE WAS PUTTING US IN SEQUENCE BEHIND OTHER ACFT. WE TAXIED OUT OF SPOT XX AND FOLLOWED TXWY M. GND CTLR GAVE US A SERIES OF ALPHABET LETTERS TO FOLLOW. WE FOUND OURSELVES ON TXWY B. WE QUERIED GND AS TO WHERE THEY WANTED US. SHE SAID; 'OK. LET ME FIND YOU...YOU TOOK 2 WRONG TURNS?' R ON TXWY M; L ON TXWY B; AT TXWY N HOLD FOR MD80; R ON TXWY N; R ON TXWY A; ETC; ETC; ETC. I BELIEVE A FEW THINGS HAPPENED HERE. FIRST; I MAY HAVE WRITTEN DOWN THE WRONG LETTERS; WAS UNFAMILIAR WITH LGA AND ASSUMED THE CAPT WHO WAS TAXIING WAS FAMILIAR. ALSO; GND DID NOT ACTUALLY SEE US; OTHERWISE SHE WOULDN'T HAVE SAID 'LET ME FIND YOU.' THE TXWYS WERE VERY CONGESTED AND INSTEAD OF PASSING BEHIND THE MD80; WE FOLLOWED. ALSO; I DID NOT COMMUNICATE WITH THE CAPT; AS I WAS UNDER THE IMPRESSION THAT HE HEARD ME READ IT BACK (BY ROTE; NOT UNDERSTANDING); BUT HE UNDERSTOOD AS HE WAS FAMILIAR WITH LGA. LASTLY; TXWY M IS A HIGH SPD TURNOFF FOR RWY 13/31 AND TURNS INTO A RAMP-PARALLEL TXWY. PERHAPS IT SHOULD BE RENAMED (S OF TXWY B) TXWY MM; TXWY MA; OR SOMETHING TO DISCERN; SO LEFTS AREN'T RIGHT TURNS; AND TAXIING IS CLRER. ALSO; GND SHOULD ALWAYS USE CARDINAL DIRECTIONS; IE; E ON TXWY B (R ON TXWY BRAVO); S ON TXWY N (R ON TXWY N); ETC. THE END RESULT OF THE SIT WAS NO HARM DONE; WE TAXIED WHERE SHE WANTED US; WAITED FOR OUR RELEASE; AND WERE ON OUR WAY. THROUGH SLOW CLARIFICATION AND COM; THE SIT WAS REMEDIED.