What are the factors to be considered while migrating to linux?

One of the first things I tell people who are considering a migration is that, yes, most likely there is a Linux equivalent to the application you use. Photoshop? Gimp. Adobe Reader? Scribus. But there are certain instances where an application has been written specifically for a purpose (or company) and does not have a cross-platform equivalent. In this case, I would say you could try running your application with Wine or you could run a virtual instance of Windows to get that app running. But this takes time and effort and, in some cases, isn't as stable as one would like (especially in the case of Wine).

If you have mission-critical applications that were created for the Windows environment (and only the Windows environment), your best bet is to avoid migrating those systems that make use of the proprietary software. Of course, if the proprietary software is Web-based, you can probably go ahead because Firefox is on par with Explorer.

This is not a question most people have to face. With Windows and OS X, you have one desktop metaphor. With Linux, the desktop choices are about as vast as the choices of breakfast cereal at your local supermarket. If you select the wrong desktop, you could wind up with a lot of confused users. But the decision isn't difficult really.

If your users are accustomed to OS X, the best choice is GNOME. If your users are accustomed to Windows XP, your best choice is KDE 3.5.x. If your users are accustomed to Windows Vista, your best choice is KDE 4.x (although be sure to skip the .0 release and go straight to .1 or better.) And the Linux desktop goes well beyond the Windows and OS X metaphors. You could really stretch your imagination and create a desktop specific to your company. But the idea behind this is that, when considering a migration, you must take into account your users and which desktop they would be most comfortable with.

Work with me here. Many companies and/or institutions benefit from using the Windows operating system in less obvious ways. For instance, some universities can offer students large discounts on software (such as Visual Studio and Office) because they deploy hundreds of instances of Windows desktops across campus. Without these installations, there would be no software discounts. So making the migration in such a case would be disastrous for those who benefit. Of course, if your institution used and supported Linux, the software would all be free, negating the need for any discount (such as student-purchased software.)

Many larger companies pay to outsource help desk support -- an ugly, but true, fact of corporate culture. If this is the case for your company, you had best do a little research before you plunge into the Linux waters. If your company plans on migrating to Linux via Ubuntu (Canonical), Red Hat, or SuSE (Novell) Linux, you're in luck and can purchase support. If you go with a different distribution, say, Debian, you won't find nearly the same level of help. There are other sources of support (such as mailing lists), but you're not going to get the level you are accustomed to.