If you like them heavily sauced, of fairly so, you can reheat in the sauce. Alternatively, you can do as Jeff suggests, using a tightly covered container or simply wrapping the whole lot in well-sealed foil. (This is just to even out and shorten the reheating process.) 300?F is fine. You can sauce before reheating or you can reheat to a lower point, open the pan or foil and paint with sauce then, reheating a few more minutes after sauce application.
The trick when reheating most meats is not to go past serving temp, in most cases, lest the meat start cooking again. Serving temp is 145-155. If you reheat in sauce, bring the sauce to a bare simmer (that should be just below 180), add the chicken (which will cool the sauce) and turn the heat down a little. Reheat without simmering (which will avoid the chicken cooking further) till the chicken is heated through (around 150-155), which could takes as long as 20-25 min, deoending on how many chicken pieces are in the pot and how cold they started off.
In a covered pan or in foil, either temp the interior of one piece or simply reheat about 20-25 min, open then pan and taste a piece for heat (you're looking for good serving temp, remember). If you haven't already sauced, you can paint sauce on now. As an alternative, while the chicken is reheating you can simmer a little sauce in a pot on the stove till it reduces by about 1/3-1/2. This thickened sauce can be painted on the chicken for the last few min of reheating. You can up the reheat temp for these few minutes (and no longer), or you can briefly run the chicken under the broiler--either way will tighten the sauce further but you have to watch it--or you can just use your pre-thickened sauce. Pre-thickening makes the sauce more sticky alowing you to paint it on more thinly but get a good bind and shortened setting time.
