Ok, assuming you have created your characters by using the dials and adjusting the morphs, for conforming clothing to fit it has to have the morphs in it. Most clothing will have, this will normally be spelled out in the clothing description from the vendor. If this is the case, select the body of the clothing, not an individual body part and go to the properties tab next to the parameters tab where the dials are. You will see a number of check boxes there under the heading when conforming. Make sure the first 3 are checked (include morphs, include scales and match end points. Hopefully this should help, but sometimes at extreme values of body morphs you still get problems, in which case you have to use other methods such as hiding body parts or using the morph brushes.