How to make sure male sperm in good condition?

Stay healthy. Make sure that you aren't eating too many processed foods. Try to increase your intake of fruits/vegatables. Fertility experts recommend sex every 24-48 hours to ensure that the sperm are new.
Good Living. Sperm count is controlled by a number of factors, some which are out of your control. If there is a specific medical cause for a low sperm count (varicocele, hormones), correcting those may help. Otherwise, proper diet, proper hydration, proper rest, proper temperature (boxers vs. Briefs), increase the interval between ejaculations, etc.