I just want to add that when purchasing a moisturizer the most important factor involves the richness of the lotion. If your skin is dry, you will want a richer cream based moisturizer.
However, if you have oily skin, you can probably use an oil free lotion or hydrating lotion that does not contain oil. But moisturizing is not as necessary because of the oil that already exists on the surface of your skin.
Combination skin can use a general moisturizing lotion but only areas where the skin is dry. Combination skin tends to be oily in the t-zone so additional emulsion is unnecessary in those areas.
A great general moisturizer is the Dramatically Different moisturizing lotion by Clinique. This lotion is lightweight enough to provide moisturizing benefits without clogging the pores.