The place has no railway station, so you will have to look for a bus from Minsk.
Mir is a rather small town and it will take you about 10-15 minutes to walk to the Mir Castle from the middle of the town where the bus stop is located. The bus stop is in Market Square - where the local market, a bank and a hotel can be found.
Take a look at one of the four UNESCO sights in Belarus. The ticket into the castle and the chapel-crypt behind it can be bought at the entrance - 100 m away from the castle gate tower.
Not far from the castle - at the parking lot - there are several souvenir kiosks with hand-made pottery and wood products. Normally the vendors know English numerals or can show the figure on a calculator.
Within a walking distance from the castle there is a Mirum Cafe with good cuisine and modern design. Beside the red St. Nikolas Church there is another restaurant, but the interior is rather shabby. Inside Mir Castle itself, on the ground floor, there is a cafe called Mir Castle that serves national cuisine at good prices.
There are at least two hotel staying options in Mir. One of them is in the basement of the castle - a three-star hotel complex that includes a superb restaurant. A more budget option that would fit an individual traveler is located in the center of Mir, near the bus station. Since this is a province hotel that is state-owned it has no web-site, but you can view the pictures and find the contact details (but not book!) here .
Nesvizh, only around 27km away, is home to another UNESCO World Heritage site.