I have a GridView and DetailsView on a page, and when I specify
<asp:CommandField ShowEditButton="True" ShowInsertButton="True" ShowDeleteButton="True" /> at the bottom of the DetailsView, I get the 3 normal buttons rendered at the bottom of the DetailsView table it creates.

This seems like poor usability to me. When my user wants to insert a new record, he or she has to first get an existing record into the DetailsView Table, then click on "New". What I would rather have is the "new" button rendered elsewhere on the page, outside the DetailsView and GridView tables. I can see what the DetailsView is creating in the HTML code ... it looks like this:
<a href="javascript:__doPostBack('DetailsView1','Edit $0')">Edit</a>

I could probably just copy this elsewhere on the page, but that is a pretty bad coding practice.

What is the preferred method of creating the button outside the GridView and DetailsView? I tried doing my own <asp:Linkbutton> but either that's not allowed or I don't understand the syntax.

you can do that using this code:
 detailsview.ChangeMode(DetailsViewMode.Insert)

this put de control in insert mode

Thanks jpacev,
It worked like a charm for me.
Any thoughts on invoking [Update] or [Insert] record button?

Figured out:

detailsview.UpdateItem(false);