As an addendum to this question, my situation is even worse: my character is level 60, and my friend has just begun. This translates in me getting 99.2% of the xp points.
Going to higher level areas would not help, because he would run into the level penalty.
Is there an effective way (strategy/ zone grinding) to help him level up fast without boring him do death? (I'm trying to make him like the game, not hate it)
There is no real way to power level someone like in other ARPG's (Diablo).
If you were to join his game as a higher level and start killing monsters, you would be getting a much higher share of the xp for being a higher level while only doubling the base xp gain from monsters. Also if you move too far away from your friend and they aren't able to keep up they won't gain any xp for monsters you killed. Both of these would probably end up slowing down the leveling process for your friend instead of speeding it up. (Wiki page on xp gain in parties)
PoE is definitely a game to be taken slowly and get a hang of all the different mechanics, spells, skill tree etc first hand. Sure you can and possibly have already told them plenty about the game but they still might not understand until actually interacting with it.
I would assure them that yes the first couple acts or so are boring on normal but the game picks up pace once you get more support gems and passive points. Just talk with them over something like Skype or curse voice just to keep them a bit more occupied while leveling and be there to answer questions they might run into.
Since you are level 60, you should have more currency than your friend. Enough to buy some leveling uniques that would make his journey through earlier levels a breeze.
Other leveling gear will depend on what build your friend is going to roll:
Casters
Trapper
Bow
Melee
Totems
On top of that, do not underestimate the complexity of this game. Play along with your friend and be there to answer his questions.
You can try, but he has to like the "grind" on his own. The best things you can do if you want to "rush":
Overall if he's new, just make a fresh char and play along, or let him come along slowly. There's a lot of complexity and depth in poe, which you only uncover if you grind... He has to like the repetitive grinding, item discovery etc. on it's own (else he'll never get into poe) so rushing a new guy may not be a good idea anyways.
You have to have the excitement of seeing a unique drop and then iding it and reading about it (then discovering that it's junk, repeat 1000 times) and be willing to continue on if you're going to get into poe.
Another option for powerleveling has been recently discussed on Reddit.
The higher-level character wears Southbound. Unless his damage has cold or damage over time components, his hits will leave the mobs at 1 hp. The lower-level character follows in his path, far enough not to trigger the experience penalty. To be fast, the lower-level character equips an area of effect skill and / or Increased Area of Effect support gem. Quicksilver flasks and Seven-League Step are recommended.
