Things like Caffeine and Nicotine can actually slow down production. Removing soda, teas, and coffee can increase your response to the breast enhancement herbal pills mentioned above. 

Other things that can affect the results will be: Stress, Sleep, and Diet. 

You would not expect to be able to run a marathon after eating nothing but fast food for weeks would you?  Your body would not be in any shape to compete.  Your body also performs better on seven hours of sleep or more and stress levels that are at a minimum.      Obviously the're are factors that no one can prepare for or keep under control, but eliminating highly stressful situations and eating a balanced diet can help promote a better response. 

Time is another factor that will play a part in results . 
You may not know how stressful your life really is, and expect a pill to change your bust in a matter of 4 weeks.  Studies have shown that most supplements will not do this.  Just like puberty didn't happen over the' course of one month, usually a breast enhancement pill will not change your cup size in a month.  It can take some women up to a full year to see a cup size increase.  Other women may see results in a matter of 2-3 months.  Each individual will respond to the' ingredients differently based on body chemistry as well as external forces already mentioned.