(This is a response to the heuristics here in Rob's post. I posted it as a comment here, but wanted a record here, as well.)
Funny, I also had some responses to your heuristics, but I usually let longer comments age a bit before posting them. I appreciate kpeetersn's comments, as they did such a great job of opening the conversation, and showing an alternate point of view. Your heuristics are marked with a dash. My comments begin with an asterisk.
(Full disclosure: I have a habit of carefully examining statements' inverse and converse, because Americans have a persistent and faulty habit of assuming if a statement is true, then the inverse and converse MUST be true. Hence the power of the media.)
-Is the direction comfortable, easy, or desirable? It is probably not from God.
*God has asked me to do a lot of things I'm comfortable with, that are easy for me, and that I desire with all my heart. Just not necessarily at times that I feel like doing them. ;o) And, the more I have listened to Him, the easier and more desirable the things He asks me to do become.
-Is the direction difficult, will it lead to embarrassment, pain, sacrifice, loss of time and money? Probably from God.
*I'd like to qualify this one by saying these are not requirements for direction from heaven. Promptings I've received have saved me from all of those things at various times, often to great extent. Our God is a GOOD Father. Yes, sometimes He asks hard things of us . . . but not always. And never does He put us through hard things that we didn't choose. If hard things come into our lives, it's because our choices brought them there, whether or not God invited us on that path.
-Does it make you feel overwhelmingly small and insignificant? Probably from God.
*Promptings can bring these, especially as someone first begins to listen carefully to God's whisperings . . . but it's not a requirement. By "overwhelmingly small and insignificant", were you trying to describe the incredibly intimate and saturated feeling of humility that comes when God speaks direction to us? One of the strangest and most beautiful things I've learned lately about humility is that it takes a tremendous amount of it from me to approach the throne of grace boldly and accept all God has to offer, DESPITE my perceived shortcomings, the fact that I didn't spend as much time in the scriptures as I know God wanted me to last week, the fact that I'm not as devoted in prayer as I might be, etc. He still wants to pour out onto me as much as I can possibly accept. It's up to me to not beat myself up, preventing myself from accepting all He's able to give me right now, this moment. And let me tell you--THAT takes letting go of that overwhelming feeling of insignificance, of stepping forward in true humility and obedience, and a tremendous amount of trust in God. And it's 180 degrees from what I thought (and was taught) God wanted my behavior toward Him to be, which was more of the sackcloth and ashes, beating myself up kind of attitude. But who wants us to beat ourselves up? Not God. Who wants us to stand, simply and without pretense, in His presence? Not only wants that, but will rejoice with us in it? Not the adversary.
-Does it make you feel like you are someone special, that you are unique or specially prepared? Probably not from God.
*I think you may have meant something more like "Does it make you feel better than everyone, or anyone, else?"
God has used me in ways I know He prepared me for (some of those times were foretold in my patriarchal blessing, others later illuminated by the Holy Ghost) . . . and when I realized that was what He was doing, I felt all of these, along with a sense of His excitement that His planning was coming to fruition. We are ALL His favorites--and thinking of it that way is just the tiniest beginning of understanding how unstinting and lavish His love is for us. He specially prepares ALL of us for the work He wants us to do. Always. Everything in our lives can be turned to His work, to His will.
-Does it feel rushed, exciting, or thrilling? Probably not from God.
*This one needs some qualifiers. "Cast yourself from this mountaintop, so God can catch you," fits nicely as one from the adversary. "Learn French so you can speak into the lives of people I will bring to you" does, as well. The difference in the second example being that I received it from God recently, and it's absolutely exciting and thrilling, (there's nothing more in this life that I could ask for than to know I'll be able to be an instrument in God's hands, no matter how simple) and I feel rushed because I know from the impression that came with His word that I don't have much time to do it. He wants me to do it now, without delay.
Fifteen years ago I had a very simple, sweet experience where my Spanish saved a lovely sister in line ahead of me at McD's from difficulty and embarrassment when it came time for her to order. That morning God told me to study the Book of Mormon in Spanish, which of necessity kicked into gear the slightly dusty Spanish-thinking corners of my brain. I was thinking in Spanish when I stopped for food on my way to class, and answering her questions, spoken softly in broken English, comfortably in Spanish is still something that brings a shine to my eyes, because she was such a gentle woman . . . and I'm so glad I was able to spare her discomfort, and possibly derisive laughter, at the hands of the rather hurried and impatient teenage McD employees that day. Remembering that experience, and thinking of this new instruction, has me pretty excited. Even if all I do is help someone understand a menu or bus schedule on a busy day in a big city.
-Is the direction towards something that you know there is no way you could possibly do it? Probably from God.
*Again, sometimes, yes. But if it's something that you can do, even easily, that doesn't disqualify it as from heaven. (Again, that inverse thing.) ;o)
As far as discerning of spirits, I've found several ways that work really well for me. The first step was realizing that complete thoughts that come into my head aren't from my own mind. I personally have to speak or write in order for thoughts to fully form, generally speaking. I can concentrate and "speak" thoughts in my own mind, but it's a very conscious thing, like speaking or writing. It doesn't just happen on its own, or when I'm doing something else.
Once I realized that, it became easier and easier to recognize the voices of familiar spirits assigned to tempt me. (Familiar spirits aren't just hanging around mediums and mystics. They are the imps who follow us around--whose presence we are accustomed to.) It took them about a week or ten days to realize I'd caught on; then things became more subtle. I rarely hear temptations in words anymore. (Right now it's mostly just straight-out spiritual warfare with emotion as the enemy's heavy artillery.) But the differences are still there. And when I hear from the adversary, those voices are easily distinguishable from the Lord's, for several reasons:
1) Timbre/quality. Satan just can't mimic the rich, full-spectrum, complete spiritual "sound" of the Lord's voice.
2) Accompanying feelings. When the Lord speaks to me, a feeling of encompassing love and calm comes along. (If I don't feel it right away, it's just waiting for me to accept it. Satan hasn't ever been able to reproduce it.) Added to that is a level of communication with each word that just can't be put into words--feelings and attitudes, emotions and thoughts, often still images, sometimes short video-like visions, and sometimes just the impression of color, shape or movement. This differs just as a single-tone melody midi file does from a live orchestra under the command of a seasoned and well-loved director.
3) Physical sensation. Promptings from God come with a feeling of balance and harmony throughout my body that begins at the crown of my head and quickly fills me. Temptations (which can be anything from the archetypical "you really DO want to see what that wine tastes like" to "She thinks I'm a lousy mom" or "I've lost every last bit of credibility with my leadership") come with little or no change in my physical state.
4) Direction. When temptations come, they originate from behind, above, and slightly to the right of my head. Communications from God originate in the very center of my mind, like the perfect flowering of the physical sensation I mentioned above as it moves through me.
I don't know if everyone feels these things. It's possible they happen to everyone, but not everyone discerns them. My mom told me when I was a child that I was a hypochondriac, had zero pain tolerance, and worried too much about how I was feeling. (As it has turned out, thanks to diagnoses in adulthood, I wasn't. There really were things wrong with me, but I didn't know how to express them with my child's vocabulary.) That said, all of that self-directed attention means that when there's even the tiniest shift, I recognize it. So, there you go. :o)