Which one is the best method or practice when we have to install OS on large number of devices (50/100) in a given time? Is it Ghosting or WDS (RIS)?

WDS is good option but network comes to play. Bandwidth choking will happen. ghost is also a good  option. Decision should be  up to your environment capabilities.

If you have proper resources and you are going to deploy Microsoft OS, WDS is the best option.

The best way is windows deployment through remote installation services server

Hello, WDS is Windows Deployment Services and is used from Windows Server2008 onwards. RIS is Remote Installation Services and was used upto Windows Server2003. As on date, if you want to install Windows on a large number of devices, it is advisable to use WDS. If you want to deploy Windows XP, you need to use RIS (Windows XP is obselete now). If you want to deploy Windows7 and Above, you need to use WDS. Also note that WDS requires all your Devices to be in that ADS Domain. Thanks

It depends on the OS you need to deploy.

If it's Microsoft Windows Vista as a minimum, then you can use WDS.

However, if you need to deploy other OS's (Mac, Linux) you would need to create one source, and ghost it over. With Ghost, you can do it either via network, or physical exchange of HDD's.

use ghost its the best way if you have many computer model you can install the Windows in one PC without install any drivers , then creat your image using the ghost and deploy it to the other PC's

Its very easy  to install os but main subject is configure os or devices which connected to computer ..according to me wds is the best answer     

WDS or you can use it through Network Boot ..

How make the Ghost can you tell me what is simple way???

I want to make the Ghost of Window XP of different modals of computers.

with Ghosting if it the same Possibilities

If you have network connectivity between systems then use RIS. That is the best solution because it is fully explain mode