I've left pieces of this here and here. But perhaps a little code would help. :)

Public Class MyWebPart
Inherits Microsoft.SharePoint.WebPartPages.WebPart

Private Const TRACE_CLASS_ID As String = "MyWebPart"

Protected Overrides Sub RenderWebPart(ByVal output as System.Web.UI.HtmlTextWriter)
Dim TRACE_CATEGORY As String = TRACE_CLASS_ID + "RenderWebPart"

Try
Context.Trace.Write(TRACE_CATEGORY, "Trying something")
' Do something here

' pretend there is a variable
Context.Trace.Write(TRACE_CATEGORY, "variable value: " + variable)

output.Write("you html code goes here")

Catch ex As Exception
Context.Trace.Warn(TRACE_CATEGORY, ex.ToString)
End Try

End Sub