Keep cool: for optimum sperm production, the testicles need to be a couple of degrees cooler than the rest of the body. Avoid tight underwear and jeans, and excessively hot baths and saunas.
Think about your job: occupations that involve sitting for long periods, such as long-distance lorry driving, or exposure to environmental chemicals such as paints or pesticides, may affect sperm quality. If this is an issue, discuss it with your work supervisor.
Manage stress: stress doesn't cause infertility, but excessive anxiety can sometimes upset the menstrual cycle. Try to reduce stress levels and give yourself time to relax.
Take folic acid: all women trying for a baby should take a supplement of 400mcg of folic acid a day to help prevent birth defects such as spina bifida.
Check drugs: certain prescription drugs can reduce the chance of conception. If you're taking regular medication, talk to your doctor.
Marijuana and cocaine can affect sperm counts.
Things you can't change
Not all factors affecting fertility are within your control.
Women
For women, the following may affect conception:
Ovulation problems: sometimes, women don't ovulate (release an egg each month) or do so only occasionally.
Reasons include:
Polycystic ovary syndrome (PCOS), in which numerous small cysts develop on the ovaries and ovulation is erratic.
The side effects of some medications, such as anti-inflammatory painkillers, chemotherapy and radiation treatment (for example, for cancer).
Premature ovarian failure (early menopause).
Hormonal imbalances

Having difficulty getting pregnant? There are some simple ways to help nature along.
If you've been trying to start a family without success, making some simple lifestyle changes may increase your chance of conception and help to ensure a healthy pregnancy. However, there are some factors, such as age, ovulation problems, sperm disorders and damaged fallopian tubes, that you can't change.
Eat well: if you're a woman, a nutritious, balanced diet will help improve your general health and wellbeing, and ensure your body is able to nourish a baby. If you're a man, healthy eating is also important for sperm production.
Choose a varied diet containing fresh fruit and vegetables, bread, potatoes, rice and other cereals (wholegrain, where possible), milk and dairy products, lean meat, fish and other sources of protein.
Watch your weight: being overweight or very underweight can disrupt your periods and hinder conception. A woman with a body mass index (BMI) of more than 29 or less than 19 may find it more difficult to conceive.
Drink wisely: the government advises women trying to conceive to avoid alcohol completely. Men shouldn't drink more than three or four units a day, and should avoid binge drinking to prevent damage to sperm.
Stop smoking: smoking has been linked to infertility and early menopause in women, and sperm problems in men. It also reduces the success of fertility treatments.
Be active: regular moderate exercise (such as brisk walking) for at least 30 minutes a day will help to keep you fit for conception and help to control your weight.

Difficulty in ejaculating is known by doctors as retarded ejaculation. Although men with this problem may be fully sexually aroused during sex and enjoying the stimulation, orgasm seems to take for ever and may not happen at all.
Retarded ejaculation (RE) can be a very distressing condition and make men feel embarrassed, isolated, confused and very frustrated.
Partners often blame themselves and feel inadequate, which puts even more pressure on the man to perform and compounds the problem.
Some men may have had the condition all their life, in all sexual situations. Some will have no problem when masturbating alone but tense up completely with a partner. Others may only have the problem during intercourse.
If you experience retarded ejaculation when you're masturbating as well as with a partner, then the cause may be physical (diabetes, nerve damage, prostate disease, alcohol abuse, prescription drugs such as betablockers or antidepressants).
The most common causes of RE are psychological, the mind blocks the physical sensations and prevents ejaculation. Your body is telling you you're ready - you have an erection to prove it - but your head may be trying to tell you something else.

If you're not overweight and eat roughly the same number of calories as you burn up daily then you shouldn't become overweight.
If you're already overweight the first thing to acknowledge is that there's no quick fix. To lose some weight you need to burn more calories than you're consuming. For most men the solution is to:
always eat breakfast
eat meals that contain more starchy foods (such as pasta, rice, bread, potatoes) and less sugar and fat
drink less alcohol
snack on fruit rather than chocolate or crisps, for example
reduce daily calorie intake by about 500 calories
exercise for at least 30 minutes on a minimum of five days in the week (such as brisk walking, swimming, cycling, running)

Should I see a doctor?
If despite these measures the weight isn't falling off, then some advice from the doctor, practice nurse or dietician may help.