When performing facial injections I prefer to achieve a natural look.  One way of avoiding over filling of the face is to make sure you see plenty of before and after photos.  I always recommend asking for photos and bringing a photo of what you looked like 10 years ago.  A major problem as we age is volume loss.  We loose fat, muscle and bone over the years.  This fat loss will lead to sagging of the face, because fat acts as a support structure under the skin.  There is deep fat as well as superficial fat.  Area that may have a lot of animation, such as around the mouth area, tend to get more lines and wrinkles.  Over filling the face may leave you with no lines or wrinkles, but it will also make people appear very artificial and overweight.  There are many fillers on the market such as Juvederm, restylane, voluma, radiesse.  A good provider will know which filler is appropriate for different parts of the face.