Simple Steps for Enabling Customer and Partner Portal in Salesforce

Customer Portal 

1.    Build ->customize->custom portal->setting->enable customer portal

2.    Manage user->profiles->customer portal->custom->clone Profile.  
     //Skip step 2 if you don't want to use custom profile.

3.    Manage user->user->assign role.

4.    Build ->customize->custom portal->setting->create new ->assign profiles.
    //Skip step 4 if you don't want to use new portal

5.    Contact object->create contact with account name-> Manage External user->enable customer user-> assign created profile

Partner Portal

1.    Build ->customize->partners->setting->enable partner

2.    Manage user->profiles->gold partner->clone Profile  
     //Skip step 2 if you don't want to use custom profile.

3.    Build ->customize->partners->setting->enable partner->create new >assign profiles.
    //Skip step 3 if you don't want to use new portal

4.    Account object->create new account->manage external account->enable as a partner.

5.    Go to contact ->select above created account->manage external user->enable partner user.

6.    Admin->mange user->create queue ->queue member->assign partner user.

Partner Portal Lead inbox

1.    Create one queue for portal users.

2.    Now on Lead list view select the Leads (For those you want to change the ownership) and click on the Change Owner Button.

3.   On Change Owner page you will able to see the dropdown Owner, select the queue which we have created above.