I have experience - thus can contribute - in Movies, Video Games and art-related material in general, having served as chief editor, project manager, journalist and webmaster, among other things. I focus on internet research, database maintenance and overall structure and consistency.
Note: Below info is more than five years old. I should update it soon.
This user has been on Wikipedia for 15 years, 4 months and 8 days.
Get your "cats" right! Per WP:CAT and WP:DUPCAT, the general rule is that when an article is included in a sub-category, then it's advised NOT to be included in its parent category as well. There are exception to this rule, when the categories are non-diffusing. Let's take examples out of video games and movies. This basically means that when a game belongs to a subcategory when at the same time to its parent category by default, then only the subcategory is added to its article (you can't have the one without the other). But there are instances when a game may belong to a subcategory, but not necessarily to its parent category, thus it's better to consider them as non-diffusing categories and treat them differently (you can have the one without the other). Examples:
General Rule: Silent Hill games belong to Category:Psychological horror games, right? They're not action-oriented survival horror games like Resident Evil. But all psychological horror games are always horror games, nevertheless. Thus, the whole series should be removed from the Category:Horror video games. - TO DO
General Rule: Silent Hill is a Konami franchise. Which means that any and every Silent Hill game is a Konami game, either developed or published by. Therefore, it belongs to Category:Silent Hill games (subcat), not to Category:Konami games (parent), for as long as it remains a Konami product.
Exception: Final Fantasy games are role-playing games, right? Wrong. There are some instances in a franchise, when a product deviates from the genre the series represents. For example there is Theatrhythm Final Fantasy which is a rhythm game. This basically means that a role-playing Final Fantasy game must belong to both Category:Final Fantasy video games and Category:Role-playing video games categories, even though the former is a subcategory to the latter, cause you can have the one without the other. And in general, all games should have a specific genre category, cause rarely all games of an intellectual property belong to the same genre. - TO DO
Exception: To put it simply, up until Square became Square Enix, all Final Fantasy games were Square products. Which basically meant that by including them in the Category:Final Fantasy video games, you did not have to include them to its parent Category:Square (company) games too. But now, the copyright holder/developer/publisher changed hands. Neither all Final Fantasy games are Square games, nor all Final Fantasy games are Square Enix games. Someone might be interested in seeing which games belong to which company group. Therefore, including a Final Fantasy game to either Category:Square (company) games or Category:Square Enix games, in addition to the Category:Final Fantasy video games, deems essential. - TO DO