I struggled over this topic for a few years, constantly wondering if I was doing God's will or following my own unctions.. and if you ( not you personally.. if one..) aren't careful the devil will use this to stop you doing anything and tie you up in knots over it. I used to think it was some kind of power you tuned in to.. but as you know, the Spirit is the Spirit of Christ, He and the Father are one. There really is no secret formula or short cut ... its a relationship and you must spend time with God in prayer and bible study etc. The more you know Him through communion with Him the more you will learn His voice. ( I speak to myself here too!) In my own walk with God, the only reason for me not walking in the Spirit was willfully sinning and not considering it bad enough to bother correcting.. or just simple laziness. Lack of effort = lack of productivity for God.
Walking in the Spirit as far as I have experienced, is when you are abiding in Christ via an active relationship with Him. It doesn't necessarily mean you don't sin, but it does mean that when you sin, you are more and more concious of it, and smaller things tend to seem worse than they did previously. Heightened conscience is one sign that you are walking in the Spirit, because when you aren't drawing on His strength your spiritual radar and moral conscience tend to be dulled. So if you ever find yourself in the place where you are knowingly sinning, but not really feeling that bothered about it, thats the time to come back to Christ and repent.. and if not truly repentant.. ask to be made repentant!!
Christ alone is our source. Him himself, not anything or anyone else.
John 6:51 I am the living bread which came down from heaven: if any man eat of this bread, he shall live for ever: and the bread that I will give is my flesh, which I will give for the life of the world.
John 6:54 Whoso eateth my flesh, and drinketh my blood, hath eternal life; and I will raise him up at the last day.
55 For my flesh is meat indeed, and my blood is drink indeed.
56 He that eateth my flesh, and drinketh my blood, dwelleth in me, and I in him.
Again, sorry for the long post.. I must stop this