Hello my friends! In this post I will give you my ideal way of leveling with some examples. A lot of it will be an assumption of what I've read from the developers post.
First I will tell you the most popular options you have to level.
1. Quest/Leve
2. Party/Mob Grind
3. Dungeons
4. PvP! (maybe) :P
Yes there are probably more but I believe these will be the main ones that most people will focus on.
I believe ARR will be the first game to be able to mix and match your leveling experiences and not be focused solely on one option or gtfo. I think too many people are used having one option because of old games mechanics that every developer is trying to follow (Copy WoW). I must admit I was a little negative about the leveling, especially when I played the alpha, but now I'm looking at the bigger picture.
With all that said lets get into what "I" believe will be the most exciting way to level.
(The Quest and Party Grind Combo) Low Level 1-15
First I will most likely do the starter quest to get a boosts in EXP to about level 15. At this point I will try to start a grind because I personally hate running around to kill 5 mobs then returning to NPC. After a couple of levels I will be running to a new camp and will focus on two things, one will be quest that are close to NPC for less downtime on running around and seeing if there is a good grind camp in that zone.
(The Dungeon, Party and Sync Combo) Mid-High Level 15-40+
I'm pretty sure I read that Level Sync will be introduced in ARR. Personally I'm not a big fan of Sync to camp at low level areas just to hit my cap level, but I am a fan of it when it comes down to doing something quite fun! So here is how I will be using the Sync and Dungeon system. Hopefully they will add more dungeons sooner than later because I'm looking forward to Syncing to a dungeon if I'm a little to high of a level. I will most likely grind a dungeon a couple times for gear and exp when I'm at the lowest level capable of entering the dungeon. Once I feel the EXP is not worth the time, I will probably go look for a new area or dungeon to level with a group. During this down time I will probably grind some quest/leve or create/join a party. (Off Note: I look forward to syncing down from 50 to lower level to experience these dungeons for other reasons than exp)
(Party Party Party!) High Level 40+
At this point all I will probably try to do is Party Grind myself to 50, maybe while doing a dungeon if available at levels between. I will only be using the sync here if my party is stuck in the limbo levels where killing the mob isn't being worth the time but knowing that going to the higher camp will result in the same amount of EXP/Hr with just more difficulty. :P Natalan is probably the best example. Hopefully sync will help us get through that limbo faster in order to reach the higher camp for better EXP. I am assuming that the leveling process will not be like it was in v1.0 where a level 50 warrior can simply PL you through Natalan. If that is the case then I believe Sync will be useful at these levels for most people.
(PvP) All levels
Hopefully they reward a lot of or decent EXP for participating in PvP. This will give everyone the option of doing something different and interacting with people more often. This will also help through those limbo levels, especially if you're not a fan of syncing either.
(My Final Thought)
This will be how I look forward too ARR leveling, but to be honest, I think leveling in ARR will be much much faster than v1.0. So for the people who want 50 fast, the Party Grind with Sync will probably be the fastest way to go. For the rest, I hope you can look past that one option and create yourself a road map of how you want to experience the game. Only advice I can give all of you is to do what you think will be the best and funnest experience. For myself it will be exploring as many dungeons/instances and party camps as I can with friends and new people while it has some challenge. Level 50(or cap) isn't the only place where the excitement is at. I trust the dev team will give us a lot of great content at all levels.
Hopefully this has helped you in some way or another. I personally can't wait for ARR, it's really giving me the feeling again that I had when I first played XI.