The following steps help you to learn the creation of halo effect in Photoshop cs
1. The first step is to open an image that you desire to make hallo effect.
2. Next step is to choose the magic wand tool form the toolbar that you have and select the background that u desire.
3. . From the menu you should go to Select>Modify>Smooth. reset the smoothness by changing it from 2 to 4
4. Click on Filter>Artistic>Neon Glow.
5. By satisfying the 4th step you can see the neon glow window appear as the one shown below.
6. Change the settings in the neon glow window till its glow looks fine for you.
7. Click ok after you get a perfect glow on the image.
8. By following these steps perfectly you can get an image with a halo effect.