First learn about vectors and vector designing (Google). Photoshop is not the most ideal software to create really pro quality logos. Illustrator and Coreldraw are the best logo making sw. Learn any one or both, and the working knowledge of Photoshop will be helpful in making great logos.
Of course you need to know about designing concepts, and also must possess creativity to be successful in this field. Also, there is huge competition in this field, so in the initial stages at least, getting job works can be quite frustrating, and very little profitable if you want to be a freelancer in the field of logo-making...
Of course, YouTube has plenty of tutorials to help.