An older issue of Men's Health Magazine had a 20 minute stretching routine that promoted blood circulation throughout the lower limbs, especially the pelvic area.
It consists of many leg and thigh stretches that included: hurdlers stretches, splits, breathing exercises, and others similar to what track runners use as a pre-run warm up stretch.
Also, a section of Men's Health also talked about doing cut/off urination sets. This involves urinating then holding, urinating then holding..etc...do this 6-10 times during one complete urinating cycle and you will promote strength in the muscles that close the tubes upon ejaculation, and you will also promote the muscles that cause your ejactulation to become more powerful.
Other methods in lasting longer include deep, slow, breathing upon ejaculation.
I use these and they work.
Also, I remember reading in past DJ threads about masturbation.
As adolesents masturbating, it has always been programmed that we must masturbate fast in order for us not to be caught by mom or dad. Unfortunately, masturbating too fast will equate to fast ejaculation while in the bedroom. Masturbation sessions should be at least 20 minutes. By holding it in for a longer period of time, you will promote strength in the same muscles mentioned in the urination exercises.
A lot of you fellas are gonna read this reply and laugh...thats cool...maybe you are ALL SOO blessed with the stamina of a Greek God.
But here's my advice...hope this helps.