That's excellent Arch, i wish you'd posted that 6 months ago! =)
+Start playing around with 3dskyboxes. they are amazingly powerful and easy to use.
+Browse through the
tool textures. There is basically one for anything you want to do, including some cool ones like block_light and block_bullets. Almost all tool textures can be made part of a brush-based entity.
+
Valve Developer Community should be bookmarked, it's usually my one-stop-shop for information on source mapping and entities.
+the input/output system in source is amazing, and fairly easy to learn. Every entity is basicallly like it's own multimanager and can interact with every other entity in your map.
+Instead of using render properties and amount for transparency, you instead use a texture with an alpha channel. You can still use render properties if you need to on certain brush-based entities if you really need too, like func_brush, but i don't know how a widespread use of these affects performance opposed to just using the proper texture.