

Stray cats vs. feral cats
It can sometimes be difficult to tell whether a cat is a stray or a feral. Unfortunately, humans are often not very kind to street cats, so even a tame and friendly cat may become very fearful and run from any human it sees.
Friendly cats will often run away from you, but then stop and watch you from a safe distance. If you speak to them in a kind, reassuring way, move very slowly, and crouch down to their level, they may be brave enough to approach you. (Opening a can of wet food is a great way to break the ice, also!) Cats who meow are almost certainly friendly -- feral cats do not usually vocalize. Try meowing to the cat, and see if it meows back!
Feral cats, on the other hand, will usually take off like a shot as soon as they see you. They act very timid and don't make eye contact.
Don't ever try to grab or pick up a cat who you're not sure is friendly. Any cat will bite or scratch if it's frightened, and since you have no idea of the cat's vaccination history, you definitely don't want to get bitten... or to scare the cat off. Try sitting down on the ground and allowing the cat to approach you at its own pace. Let it sniff your outstretched hand, and attempt to gently pet or stroke it. Usually, a tame cat will very cautiously venture up to you and carefully allow you to touch it... and then will melt into a purring puddle once it realizes you're friendly and are going to dispense some much-missed ear scritches!
If a cat you think is tame runs off and disappears, don't give up -- if you're providing food, it will almost certainly be back. Cats don't generally wander too far, usually staying in a relatively small "home" area. And don't assume a cat isn't friendly if it doesn't approach you even the second, third, or fourth time you see it -- remember, there are lots of indoor pet cats who won't come out to talk to strangers either! Sometimes there's no way to tell for sure if a cat is friendly without trapping it, so you can interact with the cat without it being able to run away. Even then, it may take a couple of days for a cat to let down its guard and relax enough to be friendly.