And lets start with one of the most useful tricks if you have hurry, and its how to skip an uninterruptible dialogue like the Greybeards when you speak with them for the first time (this trick doesn't work with some npc's like the Hermaeus Mora dialogues or Augur of Dunlain). To skip a dialogue you need to run in direction of the speaker character and he should step back, once that the character gets back to the normal position repeat untill the dialogue it's over.

This is useful too if you're hurry and you don't want to travel to another seller, and consist in attack the seller to reset their shop inventory. For this trick you must quick save (or save) before you attack the seller, once you attacked the seller load the quick saved (or saved) game and check the seller inventory.

This is more a dirty trick to level up sneak (it could be untill lvl 100), use it only if you're stucked on some mission or if you just wanna avoid the sneak normal leveling up. Using this trick might afect the game experience, so that's up to you. For leveling up sneak you need to go to High Hrothgar and sneak up to the back of any mediting Greybeard (make sure you save the game anyways), then just start to stab and sneak should level up fast (Make sure you have the sneak eye closed before stab them), if anything happens and they start to attacking you and you don't wanna load the saved game you should try sheathe the weapon and they should forgive you (this only works once I guess).

This tricks are common known but is it worth to mentioning them for they useful impact in some occasions.

• '
  The first one is climbing a high place (like a table or a rock) while your fighting, this trick just works well with melee fighters because Archers and Magicians might attack you from a distance. The trick for me not consist in stay static in a "high" place to avoid fight, you should move foward and backwards (to attack and dodge respectively) to make the trick more useful. Also it might not work in all the surfaces, try to search which is better.

• The second one is to cancel normal attack animations with a power attack, to do that correctly you must time the auto attack with the power attack, so take a look at the red bar of the enemy health and inmediatly after doing some damage to it, do a power attack. This is useful when you want to deal damage and stagger the enemy when it's low in health, or when you have a plenty of stamina, up to you. Beside of that, you can sheattle a bow inmediatly after an arrow was shooted to avoid the slow that the reload cooldown provides if you need to dodge or something.

• Another one its to cast spells safely with the "Become Ethereal" shout. This trick is more useful while you're fighting and you need to cast long spells and two handed spells in a fight, like Fire storm, Dragonhide, etc. Just use the shout and cast the spell while you doesn't recieve damage.
  Is worth to say that this shout is useful too to run without lose stamina.

And finally some honor mentions:

• If you wanna level up fast in "The golden claw" mission, go to the three stones and activate the mage stone, then buy spells to Lucan Valerius (fury, the reanimation one and oakflesh), it doesn't matter if you're not a magician, but the best thing is having the initial mage set. In the outsides of the Dungeon, kill 1 bandit (with any weapon you wanna lvl up) and use the reanimation spell on him/her (you can use Oakflesh and fury too to maximize the experience), then kill another bandit and use it again untill everyone outside dies (it depends on how much time you wanna spend casting spells with the enemy). Once you enter Bleak falls barrow you can do 2 things, reanimate one by one the dead Skeevers on the floor and then the bandit on the table, or kill the archer one and leave the melee bandit, then you climb out the table where the dead bandit is and start casting fury/oakflesh spells. It can be both but it could be quite difficult to keep alive the bandits with you reanimations attacking them (Thing I forgoted, take advantage of the bed rolls for the "rested" bonus, you will level up even more faster!). After that you'll see a tough bandit activating a trap, in my case I fight him to level up even more the stats, maybe restoration or armor if you want to tank some damage, shield if you block the attacks, Conjuration, reanimating however dead will be there, Fury (I'm not sure if it climbs out that quick as the other schools) and again, Alteration with oakflesh spell. Or you can simply avoid him an let him die. Then it comes the part of the skeevers, use the same conjuration method on the dead tough bandit, then on a dead skeever, and repeat untill the spider, you can reanimate the skeleton near the skeevers too to maximize the conjuration experience. Finally in the spider part you can spam a bow to level up Marksman, if you are out of arrows spam your destruction spells!. After that repeat as much you want the previously techniques, as I said, it depends on how much time you want to spend on the Dungeon ;^, but in any case, there are a Restless Draugr after the spike trap that it's sleeping, you can dual weild dagger/sword him in sneak position to level up a few levels of sneak.

• And the last one, there are 3 mage tricks.
  
  -If you level up destruction and use the perk points to maximize the 3 elemental damages, that elemental extra damage will affect the elemental shouts damage too (Frost breath, Fire breath, etc).
  -If you are in sneak mode you can go faster, you need to add 2 or + spells to favorites, assign them to your keyboard numbers (1 to 9) and pressing them while you walk, example: Alternate between 1 (healing for ex) and 2 (fireball for ex) constantly. You can also do something similar with a bow, If you're going to get hit by a meele enemy and you're aiming draw the bow to gain speed for dodge or something.
  -If you're an undead like a vampire, you level up restoration and unlock necromage perk, you'll be boosted. Your spells duration and strenght will increase by 50% and 25% respectively, you'll have better enchantments, increased shout damage, etc. But in counter effect, the vampire weakness to fire for example will be boosted too. http://elderscrolls.wikia.com/wiki/Necromage_(Perk) there is the link to see all the effects.

Thanks for visiting the guide, if you have some other useful tricks you wanna share or one trick didn't work for you, post it in the comments, remember, knowledge is power.