If you see a new cat outdoors, you may think he's lost.  But with many feral cats living as wildlife, and many pet cats allowed outside (without collars), proceed cautiously.  Rescuing may not be necessary or even the best decision.  Unless the cat is in danger, observe him for a few days to ensure he really needs help.  First you want to determine if this is a pet that goes out, a feral cat, or a lost cat:

Outdoor Pet Cat Characteristics.  Friendly, well-groomed cats are probably pets that go outdoors.  They're comfortable with people and may try to come inside.  Females and neutered males are usually neighborhood cats -- they seldom roam -- but intact male cats do -- so they may live far away.

Feral and Lost Cat Characteristics.  It's hard to tell a feral cat from a lost cat because pets revert to feral behaviors when they're lost and scared.  Both come out at night and hide during the day.  When approached, they can both show signs of aggression (hiss, growl, bared teeth, arched back) and will run if you make eye contact.  The differences are subtle. 

Feral Cat Options

If the cat is feral, there may already be a caregiver providing food, water and dry shelter -- and there are probably other cats living there that you don't see because they are more timid.  If there isn't a caregiver, unless you're prepared to become one, leave the cat(s) alone -- that's their home and they've adapted to it -- it's probably better than any alternatives.  Feral cats are not adoptable so removing them usually results in euthanasia.  Most major animal groups today recommend feral cat management (TNR) over removing cats -- and TNR is also the most effective and most humane way to reduce their numbers.  Here's how it works:

Managing A Feral Cat Colony

First, secure property owner permission -- feeding the cats raises their visibility -- which, without permission, may not be in their best interest.  Begin feeding meals -- leaving food and water out for about a half-hour and then taking away the excess.  Pick a convenient time -- in the daylight. It's important to be dependable and consistent.  If you're unavailable, have someone sub for you.  Feeding is a management tool -- over time you'll meet the entire colony and can monitor them for newcomers.

In the winter months you'll also want to make sure they have adequate shelter -- under a porch, a dog house filled with straw, an accessible shed or outbuilding.  Cold is not a major problem.  Cats grow heavy winter coats just like other wildlife, but have no house-building skills and can die from hypothermia if they get wet and cannot dry off.