I rationalize that nothing I do will stop a determined/skilled/equipped thief.
Once I set that aside, I'm targeting the opportunistic thief or joy rider. A cable with loops on the end, and a padlock covers it. Length of cable depends on what's needed. Run the cable around the main frame tube, then push the cable through it's own end. Tighten it down. Then run the open end through a wheel, and to an anchor point (bike rack, etc). Run it around that object, then padlock the loop on the end, to the cable itself.
Depending on the amount of slack, a determined thief may be able to finagle this off and leave with everything except a wheel. Or cut the cable and take the whole bike. But a determined thief isn't my target.