That's when you really start to earn your pay!
You do have to make time to "look for the approach plate, get the ATIS, yada yada". You can expect more or less help from ATC depending where in the world you are when it happens.
Basically, a suitable runway means long enough with usable approach facilities appropriate to the prevailing weather (so potentially no approach facilities in CAVOK). There is a lot to do in this situation and you really need to make efficient use of both crew members and any other available assets (Company Ops, ATC etc). You may or may not consider passenger convenience, commercial factors, availability of engineering support to get back out again, airport opening hours etc etc as circumstances dictate.
Happy landings!