The generic methods are used when you have a type of processing that needs to be performed on a set of classes with similar interfaces or identifications, instead of having the same method to work on classA : IClass and classB : IClass, you can define a generic method that works on both and takes IClass as a T parameter.
In my specific case, I have a method to write out structs for binary output to interface with an external application. The ToBinaryWriterBloc< T >(T item, BinaryWriter bw) where T : struct accepts any struct I need to use. ( https://github.com/ewinnington/core-minimal/blob/master/src/data/BinaryStructs.cs )
Does this help understand where a generic method in C# is used or might be helpful?
I would also recommend you have a read of the MSDN Documentation on Generics.