Level Design - Playing with the player

So far I've been focusing on the conceptualisation and creation of characters and assets for games. Now that I've set myself to create a game I started thinking on so many more aspects that I haven't consider before.
Some of the books I've read about Storytelling and Game level design bring up some point on which game developers have to engage to 'play' with the players' mind and make the game more enjoyable. More than tricks, these are mental motivations for the brain to find the game attractive and encourage the user to keep playing it.

1- Progress Measure; Experience bars or a way to record the progress is a way to evoke the notion of always be evolving. Reward the player for achievements and always get 1xp for every action.
2- Multiple tasks; Add short objectives that require a variety of actions to achieve and that the sum of these will achieve a long term one. Any complex quest must be split into important pieces so that people can feel encouraged to win.
3- Rewarding efforts; Always reward efforts (money, exp, power, skills,etc) and not only by completing, but also for trying. Avoid punishing faults.
4- Feedback the player; Always notify the user of the relation between actions and consequences, and make sure it's clear, quick and clean, this way they can understand, learn and change in a fast way.
5- Add the element of uncertainty; the magical reward of the brain. Any known effort delights people, but an effort with variable possibilities creates the sparkle in the brain.
6- Social Network; Having people comparing their efforts by commenting, participating and working together is an exciting part for the player. Creating items, expansions, patches or a user network to collaborate and keep the 'competitive' sense balanced with the comparison will be the key for a social success.

Now all of these points sounded slightly cruel at first, yet I think the correct use of these can be a small captivating option that will only compliment the story and game play of the game.
Just as I'm writing this, I've started my test of the engine and so far I love the logical approach it has. I'm surprise of how different the creation of the game itself is in relation to the character creation only.