I generally average 6-10 samples when the input is noisy. If the noise is predominately 60 Hz, then you should average the samples across 16.6 ms (one cycle), Something like -

Code:
ADCSUM = 0
For X = 1 to 10
   ADCIN 1,ADCVAR
   ADCSUM = ADCSUM + ADCVAR
   PAUSEUS 960    ; Depending on device one Convert + add takes about 700uSec
Next X
    ADRESULT = ADSUM/10