Premature ejaculation is typically caused by a hyper-sensitive penis or overstimulation. If you find that you are overstimulated the best thing to do would be to masturbate no more than an hour before you have sex. If you find that you have a hyper-sensitive penis, a penile delay spray is the safest and easiest method to reduce the sensitivity. Many doctors recommend using Promescent as it is strong and safe to use.