When it comes to RPG's, keep in mind you need one thing first for foremost.
A good story!
Seriously. An exceptional one. Your a writer before your a game designer. If the characters aren't likable in a RPG, don't have a worthy obstacle to overcome, I immediately lost interest.
Second, if your going to Merge your RPG with another Genre. Keep, at a bare minimum, a handful of RPG Elements. Saying your game is a RPG when it's actually a subpar 3rd person shooter with a moral system is bland as fuck.
Look up tutorials. Lots of them. Examine other RPG's you like. I'm going to look at Mass Effect again. Why did we have a lava filled planet, an ice planet, and a planet with ancient ruins? What were the themes of these planets and why? Look at Spiral Knights, every level has 2 themes, "Flame pit arena" Which told you it was an arena with fire monsters, and then "Cadaverous Carnivores" which told us that there's be a considerable amount of undead ahead.
Also, include something interesting in your RPG. Don't make a basic RPG game with nothing tacked onto the side. It's cheezy and uninteresting. We liked Phantasy Star 4 because it had magic AND Battle skills as a limited resource.People went apeshit over FF7 because you could combine magic, and make your characters stronger with it on your weapons and armor. I liked Tales of Phantasia because it played like a Beat-em-up.
And again, Characters, Characters,
Characters, and Characters. Tweak them to be interesting, but also tweak them so they're fun to play with. Drake(Mine, Grrrr), for example is a alcoholic magic user with a shotgun. It wouldn't make much sense for him to run into battle with a sword. On top of that, there needs to be a convincing reason why he would join the player. Perhaps he's lonely and wants to see his son's grave? Hell, your on the way there. Perhaps after finding out that his son is not buried on the corner of South and Barrington, He requests the player to help him find his poor boy.
That's my two cents. In an RPG, story is extremely important. It doesn't matter if it's Alex's adventure to save his village from demons, or if it's the player's wasteland to explore, wreck havoc, or help people as he searches for daddy. Flesh out some ideas, and make sure there's not a single plot hole in there.
Also:
LittleWings said:
Make sure you avoid too many of these: http://project-apollo.net/text/rpg.html
There's a reason why so many games use these. THESE ARE Good ideas to take from... (Well, some of them, at least.)