FIRST
SCENARIO: Creating button from custom object going to another URL
Step 1: 
      If Standard
Object: Go to Setup>Customize>[sObject]>Buttons, Links, and Actions
      If Custom
Object: Step 1: Go to Setup>Create>Objects>[custom object]>
Buttons, Links, and Actions
Step 2: Click
"New Button or Link"
Step 3: Fill in
the necessary fields
      If you wanted to
put the button on top of the page layout:
            Display Type:
'Detail Page Button'
      If you wanted to
put the button on the related list of another object:
            Display Type:
'List Button'
      If you wanted it
to be on the detail page:
            Display Type:
'Detail Page Link'
Step 4: Set
Behavior to 'Execute JavaScript'
Step 5: Enter
the code below:
      If you want to
go to a VF page:
      top.location.href='apex/VFPage'
            where:      VFPage
is the name of you Visualforce page
      Note: you can
also put parameters here if you wanted to make your page dynamic.
      top.location.href='apex/VFPage?id={!Account.Id}'
            where:
{!Account.Id} is an ID parameter
      If you want to
go to an external site
      top.location.href='http://www.noobgrammers.blogspot.com'
SECOND SCENARIO: Creating a button from VFpage to go
to another URL
Step 1: In your VF page, create a
apex:CommandButton or apex:CommandLink
                  Example:
                  <apex:commandButton
value="Go There" action="{!goThere}" />
Step 2: In you
controller class, create a pageReference method named after the action, in this
instance, it is called "goThere"
                  Example:
                  public
pageReference goThere(){     
                        // Change current
page to Location VF page
                        PageReference
pgRef = Page.Location;
                        //you can also
put parameters here (assuming you have a query of account, e.g. Id accVar =
[SELECT Id FROM Account LIMIT 1].Id;
                        pgRef.getParameters().put('Id',accVar);
                        pgRef.setRedirect(true);
                        return pgRef;
                  }// End goThere
Method
