Much is made of what a woman should be doing in order to conceive, but it takes two to 'tango'!
Although any man or woman on a healthy diet should already be taking in the right nutrients to increase chances of a healthy conception, there are supplements which some doctors recommend for men.
Zinc - This helps to boost testosterone and raise sperm counts. This is a popular supplement for men before conception and you will find small dose pills easily available (you don't need more than 50mg a day) or you can make sure you keep up meat, seafood, pulses and eggs in your diet.
Vitamin C - Not only is vitamin C useful in general health, valuable to help the body absorb iron and as an anti-oxidant, it helps keep sperm levels up and gets them swimming! Make sure your diet is rich in vitamin C from citrus fruits, berries, potatoes and green vegetables.
Vitamin E - This can be derived from vegetables, vegetable oils, fish and poultry. Again, it aids sperm 'motility' (it's 'get up and go') and can help with fertilisation.
Folic acid - This is a popular nutrient for women before conception and through to the first half of pregnancy, but is also valuable for men as it has been found to boost sperm count.
Other useful nutrients - Try popping a few brazil nuts each day - they're rich in selenium which is great for sperm function.
Whilst any nutritionist will tell you that deriving goodness from food is best, you could look for a multi-vit supplement which includes as many as possible of the nutrients listed above.
It is important to keep up protein and fat intake, but not to excess. Ensure the fats you consume are non-saturated as being overweight can be a factor in hampering the chances of successful conception.
Make sure you watch your alcohol consumption as this can deplete zinc levels and generally have a negative affect on sperm performance.