AN MD80 INBOUND TO LAX ON THE CIVET ARR DEVIATED FROM CHARTED TRACK WHEN THEY GOT A RWY CHANGE AND TA AT NEARLY THE SAME TIME.

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WE WERE CLRED TO DSND VIA THE CIVET ARR TO LAX. AT DEN WE HAD PROGRAMMED RWY 25R FOR ARR AND AS WE APCHED GRAMM INTXN WE WERE CLRED TO DSND VIA THE CIVET ARR TO RWY 24R. IN THE COURSE OF MANEUVERING; WE HAD 2 LEVELOFFS FOR TFC CONFLICTS (THE LAST BEING A C172) AND DID NOT GET THE FMS CHANGED. IN THE COURSE OF VERIFYING THE CORRECT ALTS FOR EACH DSCNT POINT; ATC ADVISED WE WERE S OF COURSE AND GAVE US A 10 DEG R COURSE CORRECTION TO INTERCEPT THE RWY 24R LOC; WHICH WE DID WITHOUT FURTHER EVENT. THE REST OF THE APCH AND LNDG WERE ACCOMPLISHED NORMALLY. THE MULTIPLE APCHS AND VARIATIONS ON EACH APCH ALONG WITH THE DISTRS OF THE DSCNT CREATE A CLIMATE FAVORABLE FOR THESE FRUSTRATING SITUATIONS. SUPPLEMENTAL INFO FROM ACN 714534: APCHING CIVET WE WERE GIVEN 2 INTERMEDIATE LEVELOFFS AND A SPD REDUCTION. SOCAL CTL THEN CALLED OUT VFR TFC APCHING; ALT UNKNOWN. WE BOTH WENT EYES OUT OF THE COCKPIT TO LOOK FOR THE TFC. I FINALLY SPOTTED A C150 PASSING 500 FT BELOW AND LESS THAN 1 MI. BY THIS TIME WE WERE PAST THE POINT WHERE THE CIVET APCH SPLITS TO GO TO SEPARATE RWYS. RIGHT AFTER I CALLED THE TFC AND GAVE HIS ALT; SOCAL TOLD US WE WERE S OF THE COURSE LEADING TO RWY 24R AND TO COME R TO JOIN THE APCH. SOCAL SHOULD HAVE GIVEN THE LNDG RWY SOONER BUT WE SHOULD HAVE ASKED SOONER. JUST AS IT'S BEEN EMPHASIZED TO CHK THE FMS FOR THE PROPER DEP RWY AT DFW AND ATL; WITH THE CIVET AND OTHER APCHS INTO LAX; YOU NEED TO CONFIRM THE LNDG RWY.