Start by going to your biggest local gun store (or two); looking and holding as many pistols as possible, find a few that fit your hand and feel good. Next research your picks, next are you: large, big, small or thin as this will more than likely impact your decision on, full size, compact/officer size, or Ultra (I hear the groans), if your hands are large an Ultra may not work and similar if your hands are small a full size may not fit.
Now look at you price point - BUT - somewhere add in a QUALITY HOLSTER and BELT (quality is not cheap and you want quality in both holster and belt). I won't even get into IWB or OWB. Somewhere along the line you need to decide if new or used is the way to go. Used you could find a Colt Gold Cup, WC, STI, SIG, or a multitude of other many fine 1911 .45 ACPs pistols available. New, much more is available but at a higher price point. Take your time - do not buy the first pistol you see!
Enjoy the hunt, best of luck. For me fit and feel in my hand is everything!
I agree with getting some hands on time(range time if rentals are offered), though for different reasons. Dimensionally, a 1911 grip is pretty much a 1911 grip; the Officers/Ultra frames are just a touch shorter, Unless you have hands like 20# hams, or dwarf hands, the size shouldn't matter much. Different grip panels (which are easy to swap out), different beavertails, arched vs flat mainspring housings or Bobtail frames will affect how the gun "feels" in the hand.
Weight, and to some extent, slide length, are the 2 biggest considerations for a 1911 carry gun for many. If the 1/2 of an inch of frame length matters for concealability, look at an Officers/Ultra, or a CCO. If weight, but not size, matters, perhaps an alloy framed Commander/4" gun. If neither are critical to you, a 5" steel gun may work...
Another consideration is body type and manner of dress. While I firmly believe that
any adult within normal size and weight ranges can CC a full size 1911 IWB, it may be less comfortable for some. I'm 5'6"/145, and it doesn't bother me. Others may not like the weight, or the longer barrel...
Finally, how important is total concealment to you; what, if any, consequences are there if someone 'makes' you carrying? While I try to be discreet when CCing, for the most part, I don't worry too much if my T shirt shrunk in the wash and I print a little. IWB conceals much better than OWB... but at the cost of some comfort. If absolute, 100% concealment is a MUST, then waist carry is out, as are 1911s. A micro 9mm or .380 in a pocket is a better option.
Good advice on carry gear, figure you'll drop another $200+ on a good belt, holster, and magazine pouch- then decide the holster just isn't right, and get another....