you'll have to consider your graphics fashion. some sprites are smooth, while some are obviously made so they are bolded outside. like FF3 vs ChronoTrigger. some games have bigger sprites than others, some are more detailed, some are bolded on the outside with black pixels, and etc etc.
well, for these RPG type sprites, just use the good old MS Paint, if you don't have Photoshop that is. if you DO have photoshop, then you can make the sprites look much better than with Paint... although it doesn't make any difference, Photoshop is mainly designed for editing bigger images anyway