How to go OOTY from bangalore

The shortest route to Ooty is to first go to Mysore (You can take a train, less than 3 hrs..134 km)

From mysore take one of the sight seeing cabs to Ooty and ask them to drop you in ooty. That is because these cabs take you through a route where bigm buses can not go. By doing this you save 1.5 hrs. The cab will take about 2.5 hrs from Mysore.

If you are hell bent to taking a train, you have to first go to Coimbatore, there is a morning train that reaches C'tore around 1'O Clock afternoon. From C'tore you have to take a train to Metupalayam, about an hour... From Metupalayam, you have a hill train to Ooty. It is a lovely ride. So three trains in all and more than double the time needed by the Mysore route...Even if you do not reach Ooty by train, my recommendation is to take a ride on the hill train for the sheer sights that it offers you...

Refer here