How to say no politely and friendly to recommendations from waiters/staffs at a restaurant/cafe? [closed]

It is not at all rude or impolite to say "No, thank you", but if you feel uncomfortable doing so, just look at the waiter and smile broadly as you say it. The staff are not necessarily offering you something extra for your benefit: they are more-than-likely instructed to do so by management to add to your bill, so even a firm "No, thank you" is not going to cause any offence at all.