What to do with customer who is not giving business after many trials ? Is it better to leave him and not to waste time or to continue working?

Keep in touch as long as you're in the same industry. u never know when you can crack him.

There is always a fix it or exit strategy. If you think that your products standards, quality and price is as per his requirement, you should put optimum efforts. If not, then try to convince the customer by conducting seminars, value addition concept, giving free samples for trials, try to find some link inside or by building relationship. If still you are not able to make it, better concentrate on other customers.

ACTUALLY WHAT IS THE MEANING OF "NO".  I WILL SAY  NEXT OPPORTUNITY. DO NOT LEAVE A CUSTOMER EVEN IF HE DOES'NT GIVE YOU BUSINESS.  KEEP VISIT HIM AND MAKE A RELATION SHIP

WITH HIM.  IT IS SURE THAT ONE DAY YOU WILL HAVE HIS BUSINESS.