C172 PLT AND CTLR MISCOMMUNICATE A DSCNT CLRNC.

Narrative

I WAS ON AN INST FLT PLAN FROM SIOUX CITY; IA; TO OMAHA; NE; ON VICTOR 159; HDG 150 DEGS; AT 5000 FT APPROX 25 MI FROM OMAHA. I RECEIVED A CLRNC TO 'INTERCEPT AND TRACK THE LOC' FOR THE ILS FOR RWY 18. I UNDERSTOOD THAT I WAS TO REMAIN AT 5000 FT UNTIL INTERCEPTING THE LOC. APPARENTLY THE CTLR (OMAHA APCH) EXPECTED DIFFERENTLY. AFTER I HAD BEEN FLYING A HDG OF 150 DEGS FOR MORE THAN 10 MINS WITHOUT INTERCEPTING THE LOC I CALLED AND REQUESTED A BETTER VECTOR FOR THE INTERCEPT. AT THIS POINT THE CTLR TOLD ME THAT I SHOULD HAVE DSNDED TO 3000 FT '20 MI EARLIER.' I INTERCEPTED THE LOC AT ABOUT THIS TIME AND DSNDED AT ABOUT 1000 FPM UNTIL ESTABLISHED ON THE GS. THE REST OF THE APCH WENT WITHOUT INCIDENT. I ATTRIBUTE THIS MISCOM TO A NUMBER OF FACTORS. THE FIRST WAS THAT I WAS ISSUED A SOMEWHAT CONFUSING (TO ME ANYWAY) SET OF INSTRUCTIONS; I HAD BEEN EXPECTING NORMAL VECTORS FOR THE ILS. I WAS ALSO NOT GIVEN A HEADING FOR THE INTERCEPT. AS IT TURNS OUT A HDG OF 150 DEGS WOULD EVENTUALLY INTERCEPT THE EXTENDED LOC BUT I DID NOT KNOW THAT AT THE TIME AND WAS NOT TOLD. I ALSO BELIEVE THAT PROCESSING ALL THE UNEXPECTED INFO HAD ME SOMEWHAT 'BEHIND THE AIRPLANE' AND THAT DURING THIS TIME IT IS POSSIBLE THAT I MISSED THE COM FOR A DSCNT TO 3000 FT. I HONESTLY DO NOT REMEMBER THAT COM HAVING TAKEN PLACE. I PLAN ON DOING A COUPLE OF THINGS DIFFERENTLY THAT SHOULD HELP AVOID THIS SORT OF THING IN THE FUTURE. I USUALLY COPY ALL ATC INSTRUCTIONS/CLRNCS WHEN I RECEIVE THEM. I DID NOT DO THIS THIS TIME PARTLY BECAUSE OF THE INCREASED WORKLOAD (I WAS IMC AT THE TIME). THIS IS ESPECIALLY IMPORTANT DURING THESE TIMES AND THIS IS A GOOD LESSON LEARNED. I ALSO HAVE BEEN DEDICATING MY IFR PRACTICE TIME TO PRIMARILY LCL APCHS. I NOW PLAN ON INCLUDING SHORT XCOUNTRIES TO OTHER ARPTS IN ORDER TO GET MORE EXPERIENCE IN THE IFR SYS.