There might be a thread already with sililar question.- I am very new to drupal and looking for a module which will allow access to a user to their individual account. They should be able to see only their data and nothing else.They should not be able to manipulate site. This shouls be done just by email verification. I noticed that admin can grant access of a user after account creation but I am looking something smooth where anyone who creates account should see only their dat and later admin can change access level. Can anyone help me here.
Drupal has only a very course access control structure for viewing content. For the uthenticated use role, you can set permission to 'access content' (Drupal 6) or 'view published content' (Drupal 7), but that's about it.
For more fine-grained access control, you need a node access control module. There is a page at the Drupal.org wiki giving an overview of node access modules. You may start by reading that and try to find a suitable module.
One particular module, named Flexi access, allows you to create access control lists consisting of a single user. This may be what you're looking for.
Disclosure: I am the maintainer of Flexi access.