What is the male  superior  or the missionary position and when it is not advocated: The basic missionary position, also called  the matrimonial position, is the  face-to-face position with the man astride.  The woman lies on her back with her  legs. 

It makes entry  easy and facilitates the man's  the pelvic thrusts.  It allows flexibility and  intercourse  can be shallow and  tender  or deep and tough, in accordance  with mutual  desires.  The only disadvantage here is  that some  women may experience  pelvic discomfort and inability to move  as most of the weight  is borne by the female  partner.

It is best to avoid   this position and the opposite of the missionary position just mentioned, i.e., face to face with the woman  above can be helpful.

What is the side-by-side position?  In which situation is it helpful: In this  position, the couple lies on the side in close embrace each keeping  their legs  together.  Variations  life lying on their side, with the female keeping her legs apart outside  the male's  legs, bringing one knee  forward on her lying partly on top of her with one of his  legs between her to give increase clitoral stimulation, can be  tried. 

In this position, as  neither  partner bears the other's  weight, it is comfortable even during late pregnancy.  For couples  where obesity is the   major hindrance, this position definitely can help them find solace in physical intimacy.  Couples of unequal  height and elderly couples may find  this position   very convenient to meet their  special needs.

Can you elaborate on the rear entry (doggie) position: Rear entry, thought  of by many as unnatural,  has been  found to be one of the most satisfying positions.

In this  position the male kneels upright  with legs together facing the females  back and the female kneels head down, with her  legs apart.  There are  lying, sitting and standing variants  to this position. 

It offers satisfying penetration, apart from leaving the hands  free for fondling the partner's clitoris and breasts.The rear  entry  position is comfortable  in late pregnancy .  It is useful  in males who suffer  from delay in reaching  orgasm (climax).

Which position do females prefer?  Why: The b4est  position would  depend on an individual's preference.  However in a  personal interrogation with more than 3000 women, if  given a choice as to which position they would  prefer, 75 percent of them preferred the female  superior position.  The female  superior position helps  in increasing stimulation in a majority of women. 

This is  because  of more contact with  the clitoris  and her ability to move freely.  Hence,  she is at liberty to choose  the position that  stimulates her most.   Moreover, this position  gives the female a sense of superiority.  She is  in command of the  situation and this confidence increases  her active participation, in a  manner she desires, thus enhancing  arousal.  It also adds  a feature of novelty.

Which position can help in deeper penetration: The basic missionary position with a  variation, i.e. face to face the man on top, with the woman raising  both her  legs high or  holding her ankles  to keep her knees  sharply drawn up, allows deeper penetration.  This is  also called Indrani Asana.

Premature  ejaculation is a common problem.  Is there any position that help in such  cases, The female superior position often helps  delay the male's orgasmic response.