Before entering a ger you should shout "nokhoi khor!" which means "hold the dogs!" Of course you're probably in no real danger of an actual dog attack, but this is how the locals ask to enter a ger. Once you're invited in, completely enter as stopping in the entryway or threshold is bad luck. When inside you will notice two large beams, which stand near the center and are the primary supports for the ger; don't walk between these two poles as, again, this is bad luck. Also, always move to the left once inside and greet the elders first.
Although the locals are forgiving in regard to dining rules, you should still try your best to behave to their standards. Rules from one region to the next vary so pay particular attention to the behavior of others, but there are a few rules that exist across the country. Only use your right hand to eat, both when touching food and when using utensils. It is also rude to point your knife at another person. The final important thing to remember is that when passing dishes, hold the dish with your right hand and use your left hand to symbolically support your right elbow. This symbolizes the vast quantity of food and is a compliment to the host.
Finally, you may be offered an alcoholic beverage to drink and you are expected to drink this, especially men, whose manhood is in part determined by his ability to hold liquor.
Generally there is no tipping in Mongolia, however there are a couple exceptions. If dining in a western restaurant or staying at a western hotel tips are expected, 10% being a fairly generous tip.
Celebrations & Events
The largest festival in Mongolia is Tsagaan Sar, which is a New Year celebration that takes place with the beginning of the spring and is on the schedule of the moon. This celebration begins on the eve of the New Year with a vast amount of eating so you are not hungry in the following year. This eating festival begins at sun down then continues the next day before sunrise. The foods eaten during this festival include mostly white foods to represent light, including milk, rice, dairy, ul boov (or biscuits), and shimiin arkhi (or milk vodka).
Drinks
Knowing the historic Mongolian diet, it is of little surprise that the most authentic drinks in Mongolia are dairy-based. Aaruul is curdled milk, himiin arkhi is a yogurt drink and when tea is offered, it typically contains milk.
Nearly every type of alcohol is available in Mongolia. Vodka is common from the strong alliance Mongolia had with Russia and various rice wines from China are also popular. The most authentic Mongolian drink is airag, which is fermented mare's milk.
There is no consensus on the cleanliness of the tap water in Mongolia. In the larger cities the water is probably safe, while in more rural areas it is most definitely not safe. Of course you may stay on the side of caution everywhere and avoid the tap water entirely. If you do decide to drink the tap water, remember that many people may have troubles adjusting to the local water as it will most certainly be different from what your system is used to.