The consensus (and my personal experience) seems to be that it's easier with speaker monitors than headphones. But some have a lot of success with headphones.

If they're speaker monitors, double check on proper placement + callibration. Slight volume differences for instance can throw it off.

Then take some time to practice ahead of starting the game - preferrably with the same sound you're about to play the game with. I do this for maybe 3-5min before starting - I check the key spots - 100%, 75%, 50%, 25% and center. Take some time and try to actually imagine the sound coming from spaces in the room. For me, the 100% is usually the center or outer edge of the speaker. 50% is about the edge of my display monitor. 75% is about halfway between speaker and edge of my display monitor. 25% is about halfway from the center to the edge of my display monitor.

Some people seem to like to close their eyes and place the sound in their head. For me it's easier to imagine it in my space. Sometimes I imagine where an actual amp would be, or trumpet, or guitar, or where the speaker playing that sound would actually be positioned. With vocals you can imagine a floating head or something haha. I think trying to imagine the sound in physical space really helps your brain start to try to locate it as it would locate things in real life.

I take quite a bit of time, usually hearing the sound loop at least 5 times, maybe 10 times, sometimes more. I sometimes try to actually look to where I think I'm hearing it in the room. With the stereohead I just think of it as pan girl x2. I try to imagine where the left sound is, and then the right, then the left, then the right. It's harder to hear the separation in some of these, so stereohead takes me a bit longer.

Once I think I know where the sound is, I don't intuitively choose where I think it is roughly on the screen. I look and assess whether it's at the point I marked mentally as 50% (the edge of my screen), 75% (halfway between my screen and speaker), 100% (speaker) etc. Once I get a sense of what position it is based on my visual space, I choose that with the cursor. I've found it easier to make mistakes when I intuitively choose where I think I'm hearing it from rather than really deliberately make sure that the location correlates to the location I'm hearing in my space and how I've charted out where the different parts of my space are in the stereofield.

Now, this is a bit of a slow process, and I SUCK at the Alien Panning game in the Olympics section. Haha. Probably cause I'm too slow with this. But it's working for me currently! I'm sure you'll get some great advice from the people who get in the 90s and 100s in that Space shooter game! (:

Hope this helps!!! Goodluck!

Oh and most important, just keep at it!

One more thing just came to mind - when the sound source is a song and not just a single instrument, they often have more stereo spread in pangirl. Listen to elements that are usually panned center - pretty much always the kick, very often the snare (though some tracks have snare doubling panned or verb which can throw that off a touch). Very often the vocals too are panned center (but sometimes have harmonies or doubles that may be panned out). The center panned elements are going to suggest the center of where the sound is placed - whereas the stereo spread may be a bit farther out of where the track is actually panned to.

Cheers (:

I guess my deal is that I now know what 45% pan sounds like, so that's my anchor (other than 90% and 0). From there I try to divide that space into smaller parts, and that is where I'm still learning. I also try to make each 'test' relative to the previous one, so if one is 60% I try to select the next one relative to that instead of 'starting from scratch'.