What is considered polite in one country is sometimes considered rude in another. In other words, sometimes you should slip (sound of slip) and sometimes you shouldn't. Learning about culture differences while you learn English is the fastest way.  To brought your knowledge of the world and become more successful. When eating, the Japanese and some Chinese are in a habit of slipping (sound of slipping) their food. By doing so they show their host how much they like the food. Westerner find eating soup this way most unpleasant. They also consider picking one's teeth and putting on make-up on the table nonoes. And when it comes to tipping, they just leave some money on the table. The ammount is up to you,  but it is usually 15 to 20 percent of the cheque.