How do I leave electrical connection of heat-sink body?
If you're not using an insulation kit then the only option is tie it to the same net as the tab on the transistor.

If you are insulating then connecting the heatsink to gnd may add to much capacitance to the circuit that's on the tab. I'm thinking of the drain of a switching FET running at MHz as an example. But, by the same token, connecting it to the tab may produce a bigger radiator of interference to sensitive circuits located close by. Leaving it open circuit may sometimes be the best compromise.

I can't envisage a reason for using a resistor to ground it but, maybe there might be a subtle benefit when insulating it instead of leaving it open circuit.