Recently I've been interested in expanding my understand of and exploring spirit work and astral work. However While I have some idea about this kind of work my understanding of the basics are lacking. Where should I start and what should I be aware of?
From my own personal experiences, the toughest thing to overcome has been learning to overcome distractions and to quiet the mind. It's very difficult to concentrate and block out idle thoughts. Practice establishing a sense of peacefulness in meditation where you can find yourself just there in a void of thought. The longer you can stay in that condition, the more receptive you become to subtle energies that normally would go unnoticed.
The Northern Tradition calls this ability as going under the cloak. It is a sort of trance state that operates by eliminating the sensory information of the current state and reality and opens up the channels for sensory information from the spiritual. Some practitioners are naturally gifted with this ability but most of us have to work really hard and train our minds to see things in a different way. Like anything else that is a skill, practice is the key. Set small goals and build upon them.
It also helps to have at least a general goal in mind, or purpose for going astral when you make an attempt. It helps set things up as far as where you reach and what experiences you encounter.
Astral travel is one of those 'you find what you are looking for' situations. So if you aren't looking for anything in particular then you just sort of... float. You might reach the right state, but not go anywhere.
Another thought is to start each session/meditation with focus on raising your vibration and/or connecting with the highest vibration energy you can. Highest state that is. The most 'good' or most positive, closest to the enlightened/christ consciousness, call it what you will.
As you grow as a person the scope of where/what you will be able to connect to will change, take advantage of it to experience the newest things that will give you the most learning.