Assuming you hav a ASP.NET Project open and are using VS.NET
just go to Project -> Add User Control
Double click on the new ASCX file that you have and then you will be taken
to CodeView namely the Page_Load Section

    protected override void Render(HtmlTextWriter writer)
     {
           writer.WriteLine("This Line Will be placed where my control is
situated");
           base.Render (writer);
    }

Compile and make sure there are no errors.
Then Go to the Web Form you wish to use the control on.
With the Solution Explorer open drag the ASCX file onto your WebForm File
Switch to HTML View and move the Control in the exact position you want it

Hope that helps.

right click and synchronoize Class View -> expand the class and