Smell
To dream of smelling something reflects your feelings or gut instincts about something.  Bad smells reflect distaste for a situation, bad feelings about something, or gut instincts that something wrong.  Something may not feel right.  Feeling that something is wrong.
Good smells reflect positive feelings about a situation or person.  Your gut instincts feel that something is good.
Consider the object you are smelling for additional symbolism.
Example: A woman dreamed of being on a smelly train.  In waking life she was put on a special diet that she didn't like and didn't feel would work at all.  The bad smell may have reflected her distaste and bad feelings about the diet.
*Please See Stinks