It is important to recognize that ejaculation is only premature if the male feels that it is; The following statements are of enormous importance:

If he feels it is premature, the ejaculation will feel weak and have no 'substance' to it. It can even feel void of any erotic sensation. The receiver my not even beware that there is an issue unless the male brings attention to it.
If he feels it is not premature, then it is just that he ejaculates very quickly. He may feel that the erotic sensation to be satisfactory. However the partner may FEEL that the ejaculation was premature.
In the case of (1) (above) it may be necessary to discover the cause of the Premature Ejaculation in order to resolve the issue. The intention would be to give the male the confidence and belief in his ability to maintain intercourse until he is ready to ejaculate.
In the case of (2) (above), the change in thoughts, actions and behaviours would be to delay the pleasure sensation so that when his partner is ready for him to 'ejaculation explosively and pleasurably.

#1 tip for males to masturbate is to learn to take your time. Males tend to masturbate secretly at first, as they are anxious that a family member - especially their mother would discover what they are doing. They also have to getting rid of the 'evidence' of their behaviour… so for this reason, a habit of doing it quickly in the bathroom is quickly established. So make sure you have time and privacy, where you can take as long as you like without fear of being discovered.

Masturbation: It is a fact that most males think they know everything there is to know about this particular form of sexual activity - but it is also a fact that most of them do not. Click on this link to download the Male Masturbation Guide.