How to do it...

1. Start your form with a header element:

<header> 
    <button name="do_something_with_the_record" 
            string="Do something" type="object" class="btn-primary" /> 
    <button name="do_something_else" string="Second action" /> 
    <field name="state" widget="statusbar" /> 
</header> 

2. Then, add a sheet element for content:

<sheet> 

3. Put some prominent field(s) first:

    <div class="oe_left oe_title"> 
        <label for="name" /> 
        <h1> 
            <field name="name" /> 
        </h1> 
    </div>

4. Put buttons that link to resources relevant for the object in its own box (if applicable):

    <div class="oe_right oe_button_box" name="buttons"> 
         <button name="open_something_interesting"
                 string="Open some linked record"
                 type="object" class="oe_stat_button" />

5. Add your content, possibly within a notebook if there are a lot of fields:

    <group name="some_fields"> 
        <field name="field1" /> 
        <field name="field2" /> 
    </group> 

6. After the sheet, add the chatter widget (if applicable):

</sheet>
<div class="oe_chatter">
    <field name="message_follower_ids" widget="mail_followers"/>
    <field name="activity_ids" widget="mail_activity"/>
    <field name="message_ids" widget="mail_thread"/>
</div>