So much depends on the instruments in your band.
The bassline I play for [i][b]Don't Be Cruel[/b][/i] bears little resemblance to that played by Bill Black ... in fact what I play is far harder (especially since I'm singing too).
The reason is that my bassline has to make up for the absence of a piano in our line-up. Much/most of the "bassline" that people hear on that song is actually the pianist's left hand, so I have to introduce those notes that would otherwise be missing.
If we're covering a number originally played by a line-up of two guitars, bass & drums then I'll try to replicate the original bassline. Otherwise, what matters is making it sound like the original, which may involve doing something quite different.