It depends what it is for: sometimes for urinary cytology in the bladder cancer follow up setting in females, you can go into the bladder with a flexible cystoscope without irrigation fluid and aspirate urine that way. For microscopy and culture,  (paediatric style) wet nappies or suprapubic aspiration may be performed. More simply, allow the patient to drink fluid freely and given time, most will urinate. Similarly a caffeinated drink such as tea or coffee may cause a  diuresis in some patients. 

Sit on the toilet, relax the abdominal wall and the pelvic floor muscles - this will lead to an opening (funneling) of the bladder neck. Don´t strain - straining counteracts the pelvic floor (bladder neck stiffer)! Maybe this simple activity helps. First  step.

Well it's again our daily feeling about this problem. But if it is really necessary i think a catherisation is indicated. Otherwise what helped in children sometime to put the hand in could water or if You have a pipe whit flowing water in the room - sometimes it opens bladdermuscel too Allthe Best Your Hainz

Yes, I agree about running water; if I wanted to encourage an individual to pass urine, I would turn the cold water tap on in the wash hand basin and then leave the toilet (room) for a few minutes to allow privacy, helping the person trying to void to relax. Sometimes leaning forward helped. I agree with the advice given by Baerbel.

Ask the patient to run the cold water and wash his/her hands

This will trigger the sense of voiding

 To Ms Mary C R Wilson                                                                                                           Well what is clear for all of us -  first in the bladder must be urine. In Germany most patients come to the docctor in the morning NÜCHTERN i.e. an empty stomach but also no liquid before (. Well that's surely not evervwhere the same. All the Best Your Hainz

First of all, I am at Al Azhar University-Cairo, Egypt.

To void without feeling the desire to urinate is more simple than mentioned.

You voluntary, decrease the acquired high alpha-sympathetic tone at the internal urethral sphincter (IUS), thus opening the urethra and urine will leak. Normally in the second stage of micturition, the mother teaches her infant/child how to keep the urethra closed all the time until there is a need/or a desire to void. This is gained by keeping high alpha-sympatheric tone at the IUS, which is a muscle-collagen tissue cylinder that extends from the bladder neck to the perineal membrane in botth male and female. 

1-   Abdel Karim El Hemaly, Laila Mousa, Ibrahim Kandil. Continence and Incontinence: How Can You Gain Contiinence? ISBN 978-3-639-66683-0, Scholars press. November 2014.

2-   Imaging of the Pelvic Floor, Abdel Karim M. El Hemaly, Laila A.E.S. Mousa, Ibrahim M. Kandil and Khaled A Shehata, Current Medical Imaging Reviews, VOL 10,3, 2014, Pp. 205-214.

3-   Abdel Karim M. El Hemaly, Laila A.E.S. Mousa, Ibrahim M. Kandil, and Abdul Kareem A. Al-Adwani. Pelvic Floor Dysfunction and its Reconstructive Surgery: Novel Concepts; Createspace, an ISBN 978-1-001-04115, Amazon Company, 2014.

4-   Abdel Karim M. El Hemaly,  Laila A.S. Mousa  and  Ibrahim M. Kandil. Micturition and Urinary Incontinence, Journal of Nephrology and Urology Research, 2014, Vol. 2, No. 1, 19-26.

5-   Abdel Karim M. El Hemaly, Laila A. Mousa and Ibrahim M. Kandil. The Concept and Pathophysiology of Urinary Incontinence; in: Ammar Alhasso and Ashani Fernando, eds. Urinary Incontinence. INTECH Publication; April 2012; 145-160.

6-   Abdel Karim M. El Hemaly, Laila A. Mousa and Ibrahim M. Kandil, Magdy S. Al Sayed, Mohammed Abdel Zaher, Magdi S. A. Soliman and Ahmad G. Serour. A Novel Concept on the Patho-Physiology of Defecation and Fecal Incontinence (FI) in Women-Moreover, Its Reconstructive Surgery; ; in: Anthony G. Catto-Smith, ed. FECAL INCOTINENCE Causes, Management AND OUTME. INTECH Publication; April 2014; 47-67.

7-   Abdel Karim M El Hemaly, Laila A Mousa, Ibrahim M Kandil & Abdul Kareem A. Al-Adwani in Pelvic Floor Dysfunction And Its Surgical Treatment: Novel Concepts On Pelvic Organs Dysfunction And Their Reconstructive Surgery, in Abdul Kareem A. Al-Adwani  eds, Al Ahram, Cairo, Egypt, Al Ahram Publication Ltd, October 2013.

8-   Abdel Karim M. El Hemaly,  Laila A.S. Mousa  and  Ibrahim M. Kandil. Micturition and Urinary Incontinence , Journal of Nephrology and Urology Research,  2014, Vol. 2, No. 1, 19-26.

I totally agree with what is said. We should bear in mind that micturation is a voluntary act that we learn to initiate even if the bladder is not at its maximal capacity.  Recently, interesting Brain imaging using MRI or even PET O15 had been published showing thé Brain areas implicated in initiating voiding

I do not understand what you mean by this sentence (You voluntary, decrease the acquired high alpha-sympathetic tone at the internal urethral sphincter (IUS), thus opening the urethra and urine will leak.).

Sympathetic system is not under voluntary control, or we could easily play with our heart beats. We void when the intravesical pressure, with or without straining, exceeds the closing pressure of the internal sphincter, followed by voluntary opening of the external sphincter.

This is the basics for timed voiding for micturation or even defecation. In normal individuals, micturation is under volontary control. Of course vegetative nervous system is not voluntary but it is influenced by volontary control. That's why micturation is voluntary initiated and inhibited. The brain integrate all these sensory influx for example we ca easily defer our first sensation of void by turning our attention to another issue. Re-education in overactive bladder is also based on this. 

The bladder contracts as the result of an autonomic reflex; We (as humankind, amongst other animals) have learnt to voluntary control or 'modulate this atonomic reflex (potty training). This is alike many other autonomic reflexes (primitive reflexes) that we are born with; e.g. eye blinking reflex; coughing crying reflex (>we learn to speak with that) etc. However the bladdermuscle (detrusor) also needs a bit of pre-stretch to be able to contract. With low volumes and little muscle stretch it is more difficult to contract because of simple muscle physiology. However contraction will not be impossible with small bladder volume and of course emtional stress 'sympatic tone' can block the autonomic voiding reflex to switch vorm storage to voiding. Probably some persons are better able to initiate voiding as others and also with normal (usual or 'good') volumes some have a problem to initiate voiding in unusual situations; 'parauresis' or 'shy voiders'.

Emptying bladder is more philosophy than natural law. Well if doctor needs urine one should give the patients something to drink ( a little bit more than normally ) and wait. Under extremely rare medical necessity you must decide a cathetherisation of bladder. But  Honorable Colleague this question is rearly complcated