I've been putting out three cups a day. One in the morning while I am out there eating breakfast, one in the late afternoon/early evening and one when I go to bed. I have a small (approx 24"x30") cage I put the food and water in to deter the birds from eating the food. The food bowl is inside a water bowl (I call it the Bowl-in-a-Moat). Ants don't cross water, so they aren't an issue. It is rare that the bowl is empty each time I go to fill it.
At least two of them know each other rather well, as they share access to the dish when they both come.
I wish I could take them in, but we already have four 'inside' cats. One is around 14, one around 4-5, and two (the babies) around 2 1/2. The young ones came from a semi wild lot. My mechanic is a cat person, and there are a handfull of cats that he lets stay on his shop property. He puts food out. If they want to become friends, that's up to the cat(s). He regularly does the trap/neuter/release, but one year they apparently missed a couple. We took two of them. They are friendly, but standoffish. They like being in your company, but look, don't touch. After two years, the friendlier of the two finally jumped up in to my lap all by herself. I still have yet to hear her make a meow. The other one talks to us a lot, but is definitely 'no touch'. She doesn't get aggressive at all, she just runs out of reach. She will come and beg for the 'string-on-a-stick' toy.
--Cats & Macs & Chocolates - Who said there is no heaven on earth?--