Found this on the net which may help. The one thing it doesn't say is that the samply needs to be at body temp, so under the armpit is perfect!
1. You will need to refrain from sexual intercourse for 3 days prior to supplying the sample.
2. Before you start to masturbate you will need to make sure that your hands and genitals are washed and rinsed thoroughly.
3. If your partner is going to assist in producing the sample then she should also wash her hands and rinse them with water thoroughly.
4. At this stage do not use any deodorants, cosmetics or perfumes as these can interfere with the test results.
5. The best time to produce the sample will be first thing in the morning.
6. You must make sure that you hand the sample into the clinic within 2 hours of production.