Hi Arun

MountainMan & MotoEdde have both really given a fair and accurate definition of 'roads' and 'navigation' in Mongolia. I agree with all they've said. (Hi Guys !).
Mongolia 'road' system is I believe quite unique, and that is the very lure that we love, it is wilderness, can be utterly confusing, is certainly unfair (if you expect maps to be accurate or if you think there may be a roadsign!!!) But is is fantastic !
You've got another co-rider in the car just get them to look where the sun is and point your car accordingly !

Seriously it is a vast country with minimal infrastructure, be prepared.
The emptyness can be an advantage, there are few towns and so most routes (valleys) we ultimately lead you to a 'major' town. There was times when we would be driving and in the distance spot a line of telegraph poles and literally you would follow the poles ! they'll lead somewhere.
It can be disconcerting at first but it's really not that difficult.

However, with all that said we did have a GPS so we knew where we were. We also used some Mongolian maps (buy in UB as Edde suggested), we used a compass ! on our laptop we had running the Garmin world map program. I updated the garmin software by subscribing to the smellybiker.com who for a small fee can supply far more detailed and sometime more accurate garmin map.
While often the route you are following is way off anything that either Garmin or the standard papermaps by utilising all these it was good enough to get you where you need to be.

Couple of times we did indeed end up having to turn around, not often but i remember at least twice routes had been washed or eroded away and we had to turn around, retrace, replan. There's always a way, you are never far from locals and their Ger Positioning System ! works a treat.

After all that if you want an idea of where we went then download from my site the garmin tracks and waypoints we created, look here :

Index of /finally/Coming-this-way

phil.