if you use the bead on power line in series,
just check the power capability of the bead. -> size of the component.
On signal lines, look-up the impedance curve on datasheet
and then use the bead with highest impedance value for
the frequency band you want to suppress the noise.
and also check the DC resistance. only critical for high current line.
I recommend the Murata's EMI solution and several white papers.