On installing Salesforce Suit following module settings need to be done :
Under settings tab you need to enter username,password and security token to setup salesforce connetion.Click on "Save".
Under field map tab choose "Drupal object "from the list for example webform and "Salesforce object" .Click on "Map object fields".
After webform installation while creating fields remember to choose "YES" under the heading "Submit to salesforce".
Under the settings of Salesforce Web-to-Lead Salesforce OID is the must which helps to integrate data from drupal webform to salesforce leads. Salesforce OID you can get it from your salesforce account details its a unique code of 15 characters.Add the webfrom fields are are needed to be mapped on salesforce fields with their field names under the heading of "Webform Field Key". and "Salesforce Web-to-Lead Form Field ".
That's it.Above steps helps you to integrate drupal webform with salesforce .Submit webform data from your drupal site and you can see it populated in the salesforce leads.