Its an overwhelming search you have started but hopefully I can help you at least get started.
1.) How do you think you are going to carry? Outside the waistband (OWB), Inside the waistband (IWB), pocket, or another location (appendix, ankle, etc). This will help you determine the size of a gun you are looking for. However, regardless of the gun you may have to adjust your dress slightly and dress around the gun occasionally to conceal it well.
2.) What caliber? I would suggest a .380 to be the very absolute minimum, though a .38 special is considered the minimum by many. 9mm, 40SW, 45ACP, etc are all basically the same considering today's hollowpoints. 9mm is generally the cheapest to shoot of all the calibers and you generally get the most rounds in the same size gun of the main calibers.
3.) What type of gun? Revolver? Semi-auto?
4.) Trigger type? Single action (think 1911), is the easiest/lightest trigger pull. Striker (think Glock, M&P, XD, etc), Double action (most revolvers and some semi autos are double action only like Beentowns Kahr), Double action/single action (Sigs) where the first shot is long double action but the shots after that are single action, and will most likely include a decocker.
I suggest you go to a range where you can rent guns and plan on dropping some money on range time. First hold all the different types and figure out what feels good in your hand or what doesn't. Then take the top 3-4 guns to the range with you and run a box or so through each. You'll figure out what you personally like.
Brands are just as bad or worse than car brands. If you stay with the major players (HK, Sig, Glock, XD, M&P, Walther, Berreta, Kahr, etc) you should be fine. Just ask here once you get the field narrowed a bit and we can help you out.