Ok, I'll start off by saying this: This article mainly targets action or adventure games, but you can still shape these ideas into any other genre.
Ok, now that that's said and done boys and girlies, we'll start with our first lesson:
LESSON 1: TAKE YOURSELF SERIOUSLY... BUT NOT TOO SERIOUSLY.
I'm sure we all love to play a game with a thought provoking story as much as the next game fan, but every once in a while, you've just gotta lighten things up a little. Take Final Fantasy for example- this game can last up to 40 hours, and over that amount of time, the misty- eyed melodrama and unavoidable deaths of party members can get a bit heavy, so, the developers have added a card game into it. Then there's the Choboco sub quests...
Also, look at Metal Gear Solid- this game's plot is so damn heavy that Kojima couldn't help but to add things like the legendary Cardboard Box, pictures of chicks in their bikini's posted on walls, and being able to strap C4 on a guards back. It's all about making things more fun, and actually it can add to the lastability.
LESSON 2: MEMORABLE CHARACTERS MATTER.
I'm sure you guys know this already, but I'll put it in anyway. In your games, make your characters unique. Don't make them an on screen picture with a bunch of stats, make them have a personality. Make their appearance look funny, cool, wierd, anything BUT original. That's why all good role players have weird characters, because it works, and it'll interest the player more. Which brings us to another matter. Make the character interact with the player. Lots. It makes the game more beleiveable, and definately more fun.
LESSON 3: GO THE EXTRA, EXTRA MILE.
I know a lot of people have trouble finishing games. Sometimes, you lose motivation. Other times, you get bored of it and other game ideas pump through your head. But I also know this: When you DO finish a game, the feeling of relief is absolutley overwhelming. Now when I say, 'Go the Extra, Extra mile', what I mean is, after you have finished a game, spend the next few days tweaking it. Go through every little section of the game and find out what is fun, and what isn't. You can improve graphics, add special effects, test for bugs, make animations better and more realistic. Just remember: You can ALWAYS do better than you already have. It doesn't take long, and the overall product can become twice as good. And one more hint: Always put yourself in the players position. Would they like this? Would they like that? Trust me. It works.