As you continue to level up, you should always get new spells and abilities any time that you can. This will ensure that you always have the most powerful versions and newest abilities and spells for your class when you head into battle. Having the best spells and abilities will only help you when you are trying to find a group for an instance, and will allow you access to more xp as you level.
As you are moving up in the ranks of the WOW GOLD, you should try to use your healing spells as much as you can. Whether it is with a group on a quest, or by yourself, you should try to use them when you can. Place your healing spells on your hot keys so they are easily accessible when you need them, because in a group situation, you'll have to use them often and quickly. You should also place these spells together and not spread them out over the different keys so you have to search for them when you need them.
 Now that you are ready to join a group, you should start to keep a constant watch on your group members' health bars. When they begin to get low, heal them. If several are getting low at the same time, you should start with the lowest one and work your way around until you have gotten them all healed and continue around again, making sure that all your group is fully healed. Make sure that you have plenty of mana drinks or potions, as you will surely need them while in an instance. And, if you have a warlock in your group, ask for a soulstone to help resurrect yourself if you die.