What should be the main point to keep in mind when estimating the time for Research and Development task. Suppose I have to estimate "ABC" task using "WPF" technology and I have no experience for it, I need to some R&D for it.
Don't give an estimate until you have had time to play with the technology. Allocate a certain time (2 days, 1 week, whatever you can get from management) to understand the concepts and write some code yourself with it, to get a sense for what the development process takes and how steep the learning curve is. Then, estimate.