the best way of finding a good cattery is to phone them and ask if you can visit them for a look round before booking,
a good cattery will allow you to do this as they have nothing to hide,
look for clean, large pens with plenty of cat friendly shelves, outside run preferable, cat flap access to inside and outside of run,
ask what thier feeding regime is, do the cats get any human interaction during the day or do they just feed and run,
they should also need vaccinations up to date for the cat if they dont ask for this then i would be worried about my cat coming home with something like flu that he didnt have when he went in, ask how often they clean the pens and change the litter trays, ask if you can supply your own food