There are programs that will cost you some dough like
Aesprite or
Pickle. I definitely prefer GraphicsGale over them considering it's available for free and compatible with many files. Personally, I switch between GraphicsGale and Photoshop whatever I'm feeling.
The best way you can learn is to look at the BW sprites, and from there you can practice and try to imitate its style because there is definitely a certain style to it compared to previous generation sprites.