The border crossing between Tashkent and Shymkent is at Map Location: 41.467018, 69.356470 and enters Kazakhstan at Zhibek Zholy.
The marshrutka minibuses from Tashkent to the Border gather on the north side of the outer ring road at Map Location: 41.383904, 69.290564 . To get there using public transportation, take the Tashkent Metro to the last stop on the green line, Shahriston, (Tashkent Metro Map) and then catch buses or marshrutkas going north.
The ride to the border only takes about 20 minutes and is almost free. The minibus stops in a market area about 500 meters south of the border. Money can be exchanged by individuals hanging around the market. There are also money changers on both sides of the border. To get to the border, follow the crowd walking straight north on the main road.
The Uzbekistan exit is crowded with people constantly trying to cut into the lines. After the exit, everyone is funneled into a fenced corridor with a huge mob of people shoving and waiting at the entrance to the Kazakhstan immigration office. Small groups are let in periodically. An immigration form must be filled out before going through immigration. The blank forms are hard to find and there are people giving out and filling out forms for a very small price. Once again everyone, especially the older women, try to cut into the lines. All luggage is scanned after the immigration check but they don't really pay attention to that. The border crossing takes at least an hour.
On the Kazakhstan side there is a big crowd of taxi drivers and money changers doing their hustle. A little farther out there are marshrutkas that leave as soon as they are full and charge around 700 tenge to go to Shymkent. The marshrutkas make several stops in Shymkent starting at Map Location: 42.306058, 69.575356 and then going close to the center at Map Location: 42.318272, 69.579397 .