Here are my experiences so far; comments and suggestions invited.

I've tried vipassana three times so far, twice for 25 minutes and once for 30 minutes (in all cases minus the time it took to go settle on my bed and turn off the nearest light after setting the timer). Roughly following the instructions in MPE, I settled in a comfortable position and closed my eyes. I tried to summon up a feeling of mettā, which is hard to do without someone in particular in front of me to direct it towards. I thought of feeling it towards several specific people, some easier and some harder for me to express loving-kindness to, and then tried to focus on the feeling itself and project that generally. I notice that when I'm succeeding, I feel very content and in control. I then took three deep breaths and began the actual breath focus, letting my breathing fall back into a natural rhythm. In all cases (sooner in the later sittings than in the earlier) I had the physical sensation of being heavy, solid, and unmoving, but not hard or dead. Like a tree stump, not like a rock. It's quite comfortable, and I expect it's related to being relaxed and still and minimizing sensory input.

The first two times, I was focusing on the rims of my nostrils, as suggested in MPE. The first time I was able to stay mostly focused on that feeling for a few minutes, and then only for a few seconds at a time before getting distracted by other thoughts reeling around in my head (both verbal and visual). I tried some of the counting exercises in MPE, which worked a little bit as long as I was still doing it, but I'd lose focus again immediately after stopping. I was pretty frustrated by my distraction, although I figured it was probably normal for a first attempt. I was less frustrated the second time; I'm not sure I had much more success in focusing, but I was more able to accept that sometimes my mind will wander and to patiently redirect my attention. Again, I tried the counting exercises, but that seemed to just keep me thinking about counting, which wasn't very satisfying.

The third time was right after I read the Developing Meta-Feeling Skills post, and I focused on the area between my nose and mouth as it suggests. I found this much easier, and I spent much more time actually paying attention to the feeling of my breath, even while other thoughts and feelings were going on. I still got distracted, but the corrective effect of pulling my attention back to the anchor lasted longer. I got the solid-feeling very quickly this time, and felt especially comfortable in it--like I was in my very own cocoon. At the same time as the physical heaviness, I felt a little bit floaty and detached, which was fun. (I imagined the light part of myself starting to drift away from the heavy part, but not far--they didn't separate from one another.) I didn't feel at all anxious, impatient, or distressed at being stuck in my own head; on the contrary, it was like being in a safe place where I had full control and all the time in the world to do what I pleased without interruption. I reflected on my day, which had been quite pleasant, and thought about why the parts that had felt good and bad had felt that way (trying not to value the pleasant more than the unpleasant, but just to understand them). I found myself half wishing I had heavier things on my mind, while I was in a good headspace for dealing with them. It was a cold, damp night out, and I would sometimes "watch" myself shiver, thinking about the sensation without actually feeling uncomfortably cold. (The ability to do that is not unique to meditation for me; I noticed a while ago that if I pay direct attention to e.g. pain I can't simultaneously be distressed by it.) At some point I noticed that it was silent out, really silent, which is very rare here even at midnight (which it was). I enjoyed that thoroughly, and was delighted by how long it lasted.

One question I have: I was expecting to become uncomfortable in the position I was sitting in after half an hour, but I didn't. Someone mentioned deliberately choosing a position that would be slightly uncomfortable. Is there a reason to do that if I'm not feeling uncomfortable anyway? Or am I only not because my sittings are still fairly short?

ETA: Fourth sitting, just now, 35 minutes. I was kind of grouchy and was hoping it would help, but it didn't. I found myself wanting to stop early. I did okay on keeping focus, but the time seemed to go quickly and I felt unpleasantly groggy afterwards, which makes me wonder if I briefly fell asleep. I felt the heaviness but not as soon or consistently as previously. I noticed at some point that I was drifting into a slight hunch, another reason to think I was half-asleep. One interesting experience was knowing my hands, resting loosely in my lap, were touching, but being unable to tell how--I wasn't getting sensory data from my fingers. I guessed that they were interlaced. Later, when I noticed I was feeling them again, it was obvious that one hand was folded around the other. This wasn't a circulation issue, there was no tingling or constriction or pain--my brain just had not been listening to what my fingers were telling it. I think this is probably how we deal with most sensory input most of the time; the odd thing was experiencing it when I was trying to feel what my fingers were doing.

When you're getting started with meditation, is it helpful to listen to guided meditations? I found some guided meditation mp3's available for download at the UCLA Mindful Awareness Research Center, and a longer guided vipassana meditation by Joseph Goldstein.

Let's say I start meditating with my eyes open and then spontaneously close them. Should I keep them close? Let's say I spontaneously start rocking. Should I keep rocking? Let's say I become thirsty. Should I get a drink, meditate on my thirst exclusively, make my thirst another thing I'm allowed to meditate on, or continue attempting to meditate on whatever I was originally meditating on?

Any thoughts about meditating while sick? Obviously breathing through the nose may not work. Would you focus on breath across tongue/lips, or something else? It's looking like I'm going to have this problem for a few days. :|

Problem(?): I do not observe any effect different to just sitting still for a long period of time. Makes me think I am not doing it correctly.

Who is interested in a Less Wrong Meditation Day? Will_Newsome originally proposed this possibility:

I was thinking about scheduling a Less Wrong Meditation Day, in a week or two after people get a chance to read up, where we choose a Saturday and everyone meditates for 6 hours, all starting at roughly the same time. You put social pressure on yourself by committing to report back with your experiences, and this way you can try out extended meditation without having to go through with the scary 10 day retreat. Lots of people won't be able to find time in their schedule, but I think a few people might, and if there are enough people then it could be good. I'm really interested in seeing the variance of experiences.

I'm curious about how fast Less Wrongers can progress in comparison to the general population. People can also use this opportunity to identify problems with their practice, which we can work together to solve.