In this video I explain what Lightmap Templates are, and how they greatly reduce bleeding of shadows, help pre-plan your UV setup and aim for proper shadow resolution sizes. I also show you something called "Pixel Snap" that will help you make perfect placement of UV Islands in the UV Editor Pop-Up Grid.
Videos I Got Info From:
Warren Marshall
Lightmapping Pt. 1
• Quick Tip #19 : Lightmapping
Lightmapping Pt. 2
• Quick Tip #20 : Lightmapping Pt. 2