In some jurisdictions if a concealed pistol becomes visible to the public, charges can be brought against you, even if open carry is legal. So keep your pistol concealed unless it is needed.
Concealment can be hard depending on the size of the pistol you choose to carry. A full size 1911 or Glock 21 can be a challenge; the flip side is a small .380 auto like the Ruger LCP that just slips in your pocket.
Holster choice can go a long way in aiding concealment of your pistol. With an inside the waistband (IWB) holster, the only part of the pistol that is above the belt line is the grip, so the length of the barrel is of no concern and a double stack pistol is less of issue. Even a heavy person can throw on a cover garment and no one will know they are concealing a pistol. Cover garments with patterns do a better job than do solid colors.
If you choose an outside the waistband (OWB) holster, keep in mind the whole pistol is exposed and a cover garment needs to be longer. Also a heavier material will help keep the pistol from printing. Printing is when the shape of the pistol can be seen through the cover garment or pocket. One must use caution when bending over and reaching above your head, as the pistol can be exposed.
Pocket carry can be a good choice if your dress is more business attire, without a jacket. Some IWBs can accommodate your shirt being tucked in, but the bulge of the holster and pistol can look out of place. You should use a holster that is designed for pocket carry and do not put anything else in the pocket. If your pants are snug fitting, a single stack semi-auto, such as a Ruger LCP or similar, can be more comfortable and less visible than a revolver when sitting down. This is much less of a problem with loose or baggy pants. For the folks that work in construction, or crawl around on the floor and under desks, pocket carry is far more comfortable. Any pistol that is carried in a pocket will need to be cleaned every two to three weeks. Lint and other debris will buildup and collect in the pistol much more so than when it is carried IWB.
Fanny packs can be a convenient way to conceal a pistol. Forget what you hear about everyone knowing you are carrying just because you are wearing a fanny pack. Look around; there are enough people that still use them that you will blend in, provided you are dressed appropriately; no slacks and button down shirts. The only way anyone would know is the little tab in the upper corner that you pull on to access the pistol. Other than by another gun person, it will go unnoticed. Also, men tend not to look at other men's waistlines and below.
For the women that refuse to be a victim, carrying concealed can be a big problem. Current styles are more form fitting and this will limit the size of pistol that can be worn on the belt, if at all. An ankle holster would work well if you wear pants that are straight legged. Skirts pose another problem; ankle holsters are out, but a thigh holster can be implemented.
One option I have heard good reports about is using a pocket holster that is suede on the outside. It sits between your body and waistband of the skirt or pants. The pistol could not be very big, something similar to a Ruger LCP, LCR or Smith & Wesson Airweight.
Off body carry such as a purse, backpack, day planner or other bag needs some serious thought. Any time you set down the bag you run the risk of leaving it behind and you are more susceptible to the bag being stolen; purse snatchings are a fairly common occurrence. When you have no other alternative but to use off body carry, be even more vigilant and think about all the scenarios beforehand.