Samarqand is a city in central Uzbekistan.
North towards Samarkand and Tashkent
Same spot as when going to Khiva, just stay on the M37 and don't change to A380. From the city centre you can get inside the bus 37 or 7 (1000 sums) going north; to the north bus station (avtovokzal). You can catch the bus in the Nisomi str.; very close to "Chor Minor". From the avtovokzal ask for the small marshrutka or "Damas" (the small white chevrolet van very popular in Uzbekistan) number 205 which goes to Romitan village (2000 sums). Ask the driver to get out at Galaosiye, one village right in the M37 heading to Samarkand.
A lot of traffic going to Navoy and Kiziltepa, but also to Samarkand. Also very doable to get to Tashkent in the same day, as there is quite a lot of traffic heading to the capital. You dont really need a truck to do long distances in this route.
NorthWest towards Urgench (Khiva) and Nukus
The hitchhiking spot is past the roundabout 30 minutes walk North of old city.