Hello everybody,
I would like to share my way of playing Rehgar. I mostly focus on Healing and supporting while staying as mobil as i can for helping each lane individually.

Level 1:
You are going to pick Spiritwalker's Grace. My choice is pretty basic here, it reduces the Mana you need to spend to heal your teammates. I'm personally not a fan of Cooldowns which are A: long and B: don't let you move during a fight like Healing Totem. The other two talents are mostly for a Damage build that some might want to use. Therefore I go for the reduced Manacost.

Level 4:
You are going to pick Feral Heart. Again, a quite obvious choice if you want to Heal and Support your team. I combine this talent with my choice from Level 1, which leads to using Chain Heal on Cooldown once the match matures a bit. Regeneration is the bread and butter as a Healer, therefore there is no other Support choice for me. The only other talents that might be viable are Farsight for scouting and Reactive Spark.

Level 7:
You are going to pick Earth Shield. An obvious choice as it is basicly a "saved" Heal due to its shield nature. You will notice that most of the talents I picked support each other and make the life easier for my team. A shield is always nice and helps in so many situations.

Level 10:
You are going to pick Ancestral Healing. This choice can be tricky as you have to decide this early if your team is good enough or not. If your team is good enough and you see that your Chain Heal is enough for Healing then pick Bloodlust to further cement your lead. Otherwise go for Ancestral Healing to save teammates, provide Area Healing with the Level 20 Talent.

Level 14:
You are going to pick Healing Surge. This is always hard for me. Healing Surge compensates the missing healing of Ancestral Healing a little bit and you will spam Chain Heal on Cooldown lategame even on minions or mercenary's. The other talent I always look at is Stormcaller as it lets you use more Lightning Shield which results in a higher Damage output for you. But most of the time you will need the Healing to not let your team die and carry the match.

Level 17:
You are going to pick Lightning Bond. It's just an awesome Talent as it grants you a Lightning shield for free with all the perks we choose so far (Shielding). This increases your damage and lets you support your team and yourself at the same time. Obviously it works on mercenary's too.

Level 20:
You are going to pick Farseer's Blessing. It increases your Level 20 talent and even gives it an Area Effect. Rewind might only be useful if you need two Ancestral Healing's in a row, otherwise its not worth it. Storm Shield is worthless to me as you have low HP anyway and a 20% from that isn't that much, though some might find it useful. For me its enough to use Lighting Shield Shield and Area Healing.

Early Game Laning:
The early game totally depends on your lane partner and team. If you get an Illidan or somebody else that needs a lot of support then you have to reduce your roaming quite a bit.
Use your Chain Heal and Lightning Shield carefully before you reach Level 4 and get your Regeneration Talent. Always be vary of ganks and protect your team with every ability you have.
Once you are more confident and your teammate can handle the lane you might want to run to other lanes, use Lightning Shield on a minion to push more or simply save a teammate while picking up a kill. Rehgar is awesome at mobility due to his Mounting ability.

Teamfights:
The Teamfight starts and you see somebody, preferably your main Damage source getting focused, give him a Lightning Shield and Ancestral Healing. Over the Teamfight always use your Chain Heal on the Target with the lowest HP, it will then bounce through your team and keep everybody alive. Remember, you don't have to be in the front, just stay behind, spam Heals and Shields while staying in Wolfform to regenerate Mana.
There are situations where you have chase or fight, if those happen you have to place the Totem before your enemy while Healing, Auto-hitting, Shielding and using your Wolfform on Cooldown to get the most out of the 100% Damage increase.

The Regeneration Talent will keep you from porting back and lets you support your team through out the match.

This is my second guide and my way to play, if you got any questions just ask me or start a discussion below. =)
Have fun playing,
Chamaeleonx