While we're on the topic, here are some more thoughts to share to lowbies in hopes you can avoid some mistakes I made while leveling (not necessarily all Warden-specific). I'm not done leveling still but these lessons still sting when I think back on how much better off I could be now had I known then what I know now! Feel free to ignore or enhance as appropriate.
1) First, something I think I did right: read the forums daily! People here are so helpful and inspiring (see the "Bogbereth FTW" and "What Can you Solo" threads), it's an eye-opener to see what you should be able to do when at the proper level. Plus go back and re-read relevant stickied topic threads as you level up, since if you are new to LOTRO and/or to being a Warden, I promise many of the acronyms and tactics in the stickies will be confusing until you get more experience and see the new gambits/masteries/tactics for yourself. Even all of my advice is in the sticky but somehow I overlooked it (or more likely, didn't really grasp the intent when low-levelled and reading so much at once).
- PS: any tips for me? What the heck is FTW? "For The Wardens"?
2) As noted above, learn to stack XoT skills, both Heal over Time (HoT) and eventually Damage over Time (DoT). Spamming the same gambit repeatedly only erases the prior maneuver's timed heal/damage pips to reset the clock. This is a Warden's best friend and only gets better over time as you can start stacking 4 HoT maneuvers in a row, or spam multiple DoTs. Get used to it early so the next gambit is simply just another button pressed on a well-known sequence.
3) Learn to kite as early as possible so it is a standard routine. Others may have different views here on when to start, and I'm no expert yet since I just learned myself.

I offer this advice since my experience says if you start learning about kiting months into your progression, it's tough to re-train yourself but it's a mandatory skill to have. You should be able to do this at level 21 once you get Fierce Resolve. Masteries far later will make this easier/faster, but here's the principle:
- Launch Fierce Resolve: 3-1-2-4 (Fist-Spear-Shield-gambit initiate). This will start a morale leech of up to 8 targets at a time. That's 8 * 23 morale (if memory serves, I am not logged in) = ~184 morale regeneration for you every few seconds. You can then start running around in circles using the E or Q keys, and will start auto-attacking with your javelin as long as you remain at least sideways to your target. Once out of melee range (this doesn't work as well vs. ranged mobs!!) they will chase you but slowly have their morale drain away while yours gets replenished like a morale vampire.
- The Shield Up gambit (2-1-3-4 / Sh-Sp-Fi) will help reduce incoming blows by raising defenses, making you a tougher target to hit while kiting around.
- Once the Fierce Resolve icon on your foes ends, re-initiate the above steps and start kiting around again. Repeat until surrounded by corpses.
NOTE: this is easier sounding than in reality (see the "Warden Panic Syndrome (WPS)" thread!), I still have lots of trouble due to WPS or fat-fingering keys which is why I recommend learning early to get used to it.
4) Once at level 22, learn to love Conservation stance. I can't tell you how many times I got stuck in a fight with high morale but no power, using Determination stance from level 12, and thus got killed since I couldn't get off gambits in time to defeat foes. I didn't learn until much later that Conservation is designed for exactly this purpose: it boosts defenses and also ICPR (in-combat power regeneration), so you can keep your power bar filling up while you use your stacked HoT gambits to keep your morale bar high in parallel. I always figured Determination = maximum ICMR (in-combat morale regeneration) = maximum morale/life = maximum survivability, but this is NOT the case. Now I only go into Determination when running away from an unwinnable battle to boost ICMR while getting whacked in the back (some here may say, "Bah! There is no such thing for a Waden and I would believe them, I have seen the screenies).
5) Do your Deeds ASAP! This was a big mistake for me. I was in such a hurry to finish quests and the epic storyline, since I loved the stories and the game is designed to move you from zone to zone smoothly as you level, that I skipped a LOT of deeds. This had 2 implications:
- I missed on a lot of "free" buffing to my character. People focus so much on stat improvement from equipping the latest armor/jewellry/weapons, but improving virtues from completing deeds (and equipping the right virtues, of course) is arguably a bigger boost to your survivability. A Rank 10 Innocence virtue mitigates -5% of incoming melee damage, for example, this is amazing - and it is in addition to any boosts from gear. You have to start it somewhere though, so start now.
- When I did realize my mistake, and went back to complete old deeds, I was way higher level than many mobs. They were thus grey to me ... which means I got no experience points from killing any of them, though it was pretty darn easy (some challenge would be nice). I can tell you it is VERY unsatisfying to kill 250 mobs for no XP on any of them, repeated across multiple deeds in multiple zones.

ONE WARNING: doing deeds at/near your level will, however, help you level far faster. So you run the complementary risk of having some quests be grey for you by the time you get to them, if you complete all deeds per zone before moving on to the next. Pick your poison (I would recommend deeding everything per zone anyway if you have the patience since you still get the story and loot from quest completion in the worst/grey case).
6) On the subject of deeds ... working on your Class deeds can double as good muscle-memory training and good ways to better learn your class. For example, once you get the deed requiring so many Shield Walls or Precise Blows (for example), start putting them into your normal fighting rotation every chance you get. Not only will trying the new gambits help you complete the deed faster through sheer repetition, but you will start memorizing the maneuver early and will understand when/how it works best in certain situations. When complete, you get a nice character buff and you know your limits/strengths better to boot, it's a double win.
7) Don't repair your gear every time you can! I did this neurotically, whether for 50 copper or 50 silver, I repaired all my gear, every time it was damaged. Someone pointed out to me recently, however, that most likely you will be getting new equipment constantly as rewards from quest completion. So if you think about it, you are spending your hard-earned money to fix up something you're probably going to replace soon anyway! One way to think about this is ... every copper piece spent repairing gear about to be thrown away in favor of free new gear is an extra copper piece away from owning your horse at level 35. Since you need something like 4.5 gold for a horse, you can see the hill you need to climb and why conserving cash now will help later on!
NOTE: This doesn't apply if your gear is damaged/broken (yellow or red), fix that right away. Come to think of it, this habit is hard to break - I still keep repairing everything at level 53 (so expensive!!) though I am still upgrading my gear fairly often. Gotta re-train myself!