Registan is the place why so many of us foreigners come to Uzbekistan. This is a unique cultural and religious monument.
Make sure to get your guide. Right after you purchase and enter the complex, on your right there will be a booth where you can get a guide. A tip would be to test their english. Because some guides speak great english, while others struggle which makes the whole experience unbearable.
Also try to visit early in the morning when there are few people. In the evenings the lighting of the complex is majestic and one should certainly get back to see that in the evening.
The parking lot is right across the complex.
One of best sightseeing architecture in Samrkand, best to vist during light shows at Fridays. Intriguing architecture great activity zone in the complex.