The best thing to do would be to get hold of your local animal rescue society to ask for advice. Feral or stray cats frequently find food in restaurant dumpsters because they are left open and then only cleaned out once they are entirely full. If you find that a dumpster at your neighbourhood restaurant appears to be attracting feral cats, discuss the problem with the owner of the restaurant and see what strategy can be found to ensure the trash is secured.
To attempt to trap a feral cat, bait a trap with cat food, the herb catnip (irresistible to cats but not to other animals), and also tinned fish such as anchovies, tuna or sardines. Food may be put inside pantyhose and tied onto the trap so they aren't able to stand outside to haul the food out, alternatively, place it beneath the trap. Once caught, call an animal rescue society to collect the cat.
Regarding contact with feral cats: it is recommended by most veterinarians that it is best to avoid contact with stray cats or any stray animals. This of course includes holding, touching as well as feeding or caring for them or even transporting a stray. This is due to that fact that stray animals may be carriers of rabies or transfer other diseases and should therefore only be dealt with by an experienced animal control official.
Feral cats have a hard life which is not at all like the life a cat who is a pet enjoys. They can suffer from illness, parasites, injury, hunger and have to put up with people who are cruel to them as well as predators. Traffic also presents a daily problem for feral cats who live in parking lots and find dumpsters to scavenge from. Kitten deaths are estimated to be fifty per cent.
When feral cat colonies are taken away by animal control officials, they as well as the kittens are euthanized immediately. The reason for this is that even the feral kittens are unadoptable as they are competing with tame kittens for a home and many cats that are already tame are also euthanized due to a lack of available homes.