Some might get upset at me for saying Angels and Demons are not separate from us, they are not outside ourselves. I have explained exactly what they are in the Enochian Magick article. There does exist outside ourselves astral entities, and that is a whole different matter. Also the Archangels which have been invoked and empowered over many many years have also become astral entities themselves, but humans created them. The Angels and Demons that others have created, just like Deity Archetypes, can be invoked so you can benefit from their attributes. However this is not a pure way of working with magick, as you are using entities others have created and it can never be as pure as something you create yourself.
Within each of us their exists our Higher Self, or as some call it, Holy Guardian Angel or Future Magickal Self. You first have to find out it's name, and yes it does have one, and it has a symbol key that is used to invoke it in the beginning. First you find the symbol, but you probably won't even realise it is the key to your Higher Self until later. Once you have realised this is your key, you use it everyday to invoke your Higher Self, until eventually you will be given their name. Your Higher Self can be male or female, or either.
Once you have your own Higher Self's name, or Holy Guardian Angel, it is the most powerful thing ever. I sometimes forget just how powerful. The other day I had lost my purse, and I couldn't remember when I had it last. I thought I might have left it at the Vets. I looked all round the usual places. I was just about to give up and ring the bank to say I lost my card. Then I stopped for a moment and I called my Higher Self by name to tell me where it was. I was told to look in the office, and there it was sat on my desk. I never put it there! and would never have thought about looking there! but my Higher Self knew. I thanked my Higher Self and sent her love and adoration, this is important.
Until someone has this connection themselves, they won't understand this, but I can assure you it is possible and it is most amazing thing ever, and not just for finding stuff, all kinds of things that have to be experienced for yourself, words can not describe it.
Now of course a Christian's mind set will be, 'oh my goodness she has been possessed by a demon'. They have cut themselves off from true spirituality by believing the Divine and evil are something outside themselves. A Gnostic Theolalite has learnt to look within.