What is the most relaxed way to record?  I mean guitar or any other instrument, including vocals.  I like recording guitar on a portable Zoom recorder for ideas...I can upload it and fit it to a time...I can even make it sound decent with a limiter...For a guitarist like me, I think this is probably a good solution to having to create in front of a live mic.  Of course, there are additional methods of relaxation, but just try turning the recorder on and just play and play...there will always be something salvageable...even if it sucks...especially if it sucks...Think of the first recordings made by The Who...they sucked, but they sucked in a good way...people are always trying to put us down...

The most relaxed you could get would probably be via immense preparation. I don't record myself writing, maybe I should but that's just too much to weed through looking for the good bits for me. 

For me the biggest factors in making the recording environment relaxed are a) doing it alone and b) completely ignoring the clock.
 
Try being relaxed and creative while watched through glass by six other people, one of whom is visibly annoyed by every re-take, two others are debating Metallica vs. Megadeth, and another is pacing because he's the one paying the hourly rate. 
 
My #1 self-relaxation technique: telling myself it doesn't matter if it gets done today.
 
 
 

Always have mics out. Never embarrass anyone with tapes you release. You will earn trust and comfort will follow.

I also don't try to be too serious, while instilling good habits at the same time. For example, I discourage talking before the last note fades by teasing those that always jump in with their opinion.

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Insane amounts of practice then some test tracks. Listen back then another insane amount of practicing/rekerjiggering then more test tracking.
 
Repeat as often as necessary until that schtuff is as smooth and natural as breathing.
 
Also, memorize your keybindings so you can engage/stop record transport with your eyes closed. Better yet set up a MIDI transport controller.
 
JMO

Oh, and make sure as you go you get your backer tracks up to snuff wherever possible.
 
Example: If you just plugged in a simple beat and/or bass line to write to but intend on fleshing them out more later... well once you get your parts "written" and have some decent test takes (I will generally comp together the best version of my first round of takes to work with) then get right in there and finish your rhythm section (or get it closer to what you envision the final product to be).
 
It's like a back and forth for me. Start simple with the rhythm section, flesh out the riffs/vox/other melody/ornamentation. Go back to the rhythm section and fancy it up based on what you wrote on top. Then go back to the guits/vox/keys/etc and fancy them up. Just back and forth until you have something you are happy with.
 
Then rerecord EVERYTHING for the final. At that point every note/beat/cadence/whatever will be drilled deep into your subconscious, your muscle memory will be wrapped around the tune and for any "improv" parts you'll be able to launch into them much more smoothly because you aren't getting all wound up in the back of your head about what's coming up next (or what you may have mucked up before).
 
I treat my "pre production work" as if I were rehearsing/writing with a band. Just constantly working out little nuances and getting more and more comfortable with the tunes.
 
Anyone who's played in live, gigging bands can tell you that after all the pre tour prep and then actually playing the material live night after night for x amount of weeks/months that once you get back home the songs/band will be RIDICULOUSLY tighter/stronger/more confident/relaxed. And that's exactly how I treat material I'm working on here by my lonesome now that my gigging days are over.
 
And some may say that for chaotic/ecclectic music that that approach sucks the spontaneity out of things. I think the opposite is true. To truly be able to slam out some freaky deaky crazy person music that ebbs and flows and harms the listener's soul it is much more effective if all players know exactly how the other band members are going to react to random changes on the fly. Like with free form jazz jams and the like.
 
I probably don't work or write like many others these days though so that may not be all that useful.
 
I just hate half arsing these things.

I remember that Steely Dan 'Making of Aja' doc, where they talked about getting the band so tightly rehearsed that they'd eventually play 'past' their parts, in other words, the tune was 2nd nature to them by then so they relaxed and started to get the feeling into it.
 
I try and do that in a small way (pretty much what Beepster and Steve are talking about), getting the parts right under my fingers so that I feel there's time to get the nuances in and not worry about screwing up.

jamesg1213
I remember that Steely Dan 'Making of Aja' doc, where they talked about getting the band so tightly rehearsed that they'd eventually play 'past' their parts, in other words, the tune was 2nd nature to them by then so they relaxed and started to get the feeling into it.
 
I try and do that in a small way (pretty much what Beepster and Steve are talking about), getting the parts right under my fingers so that I feel there's time to get the nuances in and not worry about screwing up.

Absolutely. That's where (IMO) the magic REALLY starts to happen and the artist can let loose. The bands I played in that I felt were the tightest, yet most "free", were the ones that practiced at least 3 times a week. Anything less than that it was essentially just upkeep/prep of the basic material for the next gig. It's kind of why I eventually got so frustrated playing in live bands because there was ALWAYS some dumbmuckery preventing the acts from reaching their full potential.

stevesweat
[...] too much [...] weed [...]

That will do it.