Started a cleric awhile back up to 19 and looking to start doing LDON stuff. Mostly to now I have been grouping for fast exp, but now my role is starting to become important but having never played a cleric I have a few questions or need some tips.
1. should i buff all members in group or just MA?
2. To conserve mana have you found healing or heal over time to work better?
3. Should i bother with nukes or save mana for heals.
4. Basically wondering some playing habits others have formed to help me become a better cleric.

Does anyone have a problem asking rangers and pallies to heal themselves between fights or do they need mana for pulling and buffing themselves.

I have other characters but have never played one with a single roll like this before and any easy advice would be helpful thank you much.

1) What level are you now? You said level 19 but I am guessing you havent leveled high enough to cast Temperance. Generally when I find a group with my lower level characters (working on 28 rogue currently) MOST people have Temp already. In my opinion if you join an LDoN group and dont have Temp, youre not a team player especially if youre a melee. It is cheap and easy to get Temp so make them do it before you agree to group with them. Youre the cleric, youre the hardest class to find for an adventure, they need to come prepared to fight. Eventually you will be able to Temp/Virtue your group but most of your current buffs dont last 90 minutes like Temp and you wont have time or mana to rebuff mid adventure.

2) Depends on youre style of play. I CH the tanks and HoT the rest unless it is a caster going down fast and needing a quick heal. You cant CH yet but you can use your biggest heal til then. If youre in a fast killing group and mana isnt a problem because you have a shammy or druid along who is healing, I wold HoT the tanks when mana is good but LDoN is all about mana managment, dont waste it.

3) Heal Heal Heal... You have 2 jobs, Heal and Stun. Keep an eye on when those caster mobs begin to cast and pop off a stun. Your tanks will thank you and you will have more mana because that low mana cost stun interrupted the mob from nuking your tank for 400 points requiring you to use a high mana heal.

4) When I was lower level on my cleric I had heals memmed and every stun I could mem even at the expense of not having an Aura spell available. You have armor, dont be afraid to take a pounding and using your stuns will bring some aggro if you chain cast them on a mob. At higher levels you will swap stuns for Aura spells because you have less stuns at your disposal but for now, I would have every stun available and remember the level 5 stun doesnt break mez.

Good luck

1. should i buff all members in group or just MA?
As an experienced Cleric(63 now), i buff all group members that do not already have the same of better buffs.... some folks mention that you should tell your tanks to get temp... one thing to remember is that temp only last 90min... and most likely will still run out before the adventure is over... so be prepeare to full tanks when they need it... i would also suggest that you fully buff yourself so that you have the buffs timed.

2. To conserve mana have you found healing or heal over time to work better?
for mana management, i do not find much difference between the 2 heals... however i do find that if the char is not getting hit much, then i use a HOT simply due to the low agro nature of the spell.

3. Should i bother with nukes or save mana for heals.
I do nuke and stun when needed, or i have sufficeint mana... I rarely nuke on the first couple of mobs (i need to see what kind of group i have)... if i am not healing on everyfight, then i feel i am free to nuke as long as i am over 80m... also keep 1 to 2 stuns up for those healing mobs (i dont worry about other casters too much, but healers get my wrath quick; other rules fly out the window when facing a chealing mob)...

4. Basically wondering some playing habits others have formed to help me become a better cleric.
I would suggest also keeping at least a root(situational, if you have a good mezzer in group can drop this one) and DA/DB up... DA/DB WILL save your life when you draw agro (and you will draw agro at times; better to take agro from the tank than to let him die.. so heal tank and take agro, then DA/DB and let him take agro back)

Regarding Heal Over Time (HoT) -vs- Greater Healing (GH):

As I'm sure you did. . .I pulled out the calculator and did the math. Officially Greater Healing is a hair more efficent than Celestial Heath (assuming you have an Improved Healing focus item).

HOWEVER, in practice:

Every minute casting means one less minute med-ing. Over the last few levels, I've seen that HoT cast on my tank at the beginning of a fight often means I can sit the ENTIRE FIGHT. That in and of itself makes the efficiency calculations go out the window.

HoT reduces your chance for agro. Any time your tank does not have a proc-ing wepon, use HOT (yea, you probably knew this already).

At 36, I now use Celestial at the begining of most fight and sit out the remainder. It's helped tremendously with my mana management.

I'm sure this will all change once I get CH, but until then, I'm using HoT more than I used to and my groups are happier because of it.