Relation module tutorial I could not find good quality of tutorials on Internet for learning Relation module . Could anyone suggest some links for good documentation/tutorial for relation module ? Thank you .
Well, there are a number of screencasts available on the module project page as well as the official module documentation. Assuming you've already tried these and still need help, there are two possibly less obvious places you can go for 'tutorials':


Look through the source code of the module. Many of the more popular contrib modules have excellent documentation in the source on how to use the specific functions, methods, etc.
Scan the issue queue for relations. Other users may have some of the same questions you have (especially issues filed under 'support request') that may be of use to you. 


Finally, most modules won't have really useful tutorials on how to use them and rely on the user community to help each other define what is needed. One of the best things you can do to help is to ask questions as you explore the relations module, either here or on Drupal.org, as others may have the same questions. As you get more confident, you can help by adding some of your experience back as a tutorial for other beginners.