This instructional video will tell you how to make your first map for Counter-Strike: Source.
A higher quality version is available here: rapidshare.com/files/21334653/tutorial1_03.wmv
* By 'return' I mean 'enter.' *
If you can only see the wire-frame of brushes or solid colour instead of texture in the camera view your camera is in the wrong mode. Click on the word 'camera' in the top left of the camera view and select '3D Shaded Textured Polygons' from the menu.
If Source SDK will not open or if you cannot select the game you wish to map for try the following:
Right-click on Source SDK in your Games menu, click Properties then Launch Options and type in "-engine ep1".