I got my college education in Xian. I went back there two years ago and toured a number of places and was cheated a little. For people who want to tour Xian but do not wanted to be cheated, I can offer a few suggestions:
1. 兵马俑 is a must-to-see place. The other sites near 兵马俑 are either too expensive or not worthy to see. To go there, you take a tour bus near Xian Train Station. I forgot the cost (maybe about 15 yuan). It stops only once before reach 兵马俑. You buy your own ticket and walk yourself.
2. Xian City Wall is another site worthy to see. You go to the south gate to buy ticket and you could walk on the wall as long as you want.
3. Shaanxi Museaum which is near Dayan Ta. For those of you still have Chinese residence card, the entrance if free. Not sure about tickets for foreigner. (I did not go because of no time).
4. Evening music and water spray show at Dayan Ta. It is an half-hour light-water spring show starting about 8:30 (not too sure). It is beautiful with Dayan Ta as the background.
I agree that Xian's public transportation system is not very good. You have to stop Taxi at certain places. Really need to be careful with the BLACK "taxi".