Actually the best known way to communicate with spirit guides is to allow them to come to you when they feel necessary and listen to them. Meditate and speak, nothing more to it.
Astral projection is an elaborate and unnecessary way to communicate with etheric entities.
The ethereal beings you are referring to as dragons don't often appear as guides specifically to people so if you specifically want help from them you could try calling one or evoking one.
Of course astral projection is a possibility but still unnecessary.
This is a great question and I actually suggest the most basic of all practices, meditation. Meditation assists you in settling your mind and focusing staying open to what you experience. Besides that it's all you.