Here are some things I was ignorant about until a few years ago, when I realized I'd have to lose a few pounds or buy a new set of pants, which was followed by some successful self-experimentation.

Unless you consciously discipline yourself, and unless you're extremely athletic or have unusually low appetite, you'll end up consuming way more calories than you spend. It depends on your metabolism whether these will end up stored as fat, and in what proportion. For many people, this proportion is near zero, but only until some point in life. For me, this point came sometime in my late twenties.

One wrong-headed belief many people have is that they'll lose weight just by exercising. The trouble is, you can burn a significant amount of energy by physical effort only if you're in a great shape to begin with; otherwise, you can exert yourself for hours and still burn what amounts to (literally) just three or four bites of food. The key is to figure out a regime of exercise that makes you eat less, not more, which I managed; I'm not sure if this is possible for everyone, though.

There are insane amounts of sugar in almost any sweet-tasting drink, more insane than most people perceive them to be even if they've read the figures on the labels. (I don't really perceive those awful artificial sweeteners as "sweet.") The pictures on sugarstacks.com are worth checking out. One would do well to develop a feeling of disgust towards anything that's liquid and sweet-tasting. All this holds even for the hip and supposedly healthy pure fruit juices.

Carbonated water can be a fairly satisfying zero-calorie substitute for sweet drinks and beer. Try looking for Eastern European brands that are sold in ethnic deli stores. They're far superior to anything mass-marketed in North America.

Losing even a modest amount of weight can dramatically lower your alcohol tolerance. After losing something like 11-12 pounds, I realized that it took about half as much booze as before to get me drunk, and caused more severe hangovers. (Some of that was also due to less drinking in general during these months, but this can't possibly account for the whole effect.)

(This one I'd known even earlier.) Chin-ups are by far the most cost-effective way of working out for people with very little time and/or willpower. Just a doing a few sets every day every now and then while you're going around the house is enough to see rapid results. Again, this might be a genetic quirk of mine, not a universal law.

I guess for the topic of this forum, I should ask whether you were objectively looking for forum attitudes either way, or whether you set out to seek negativity and, with confirmation bias, found it?

I was expecting a post questioning who/what is really behind this project to make paperclips invisible.

I'm not interested in a relationship in which I can't interact honestly with the woman, because I wouldn't find it to be fulfilling. I'd rather be single than have to tiptoe around my romantic partner's irrational beliefs. Changing that implies either ceasing to care about rationality, or dramatically lowering my expectations for a relationship. Neither of those sounds particularly appealing.

I'm sure that part of it is because there's an awful lot of things in this world to be negative about.

This seems like very good, thorough, general advice. However, I wonder how many of us (heterosexual males reading Less Wrong) have romantic preferences that are as general. I realize that the "reading Less Wrong" part of that descriptor wasn't specified in the question, but it seems implied.

In general, a heterosexual man might describe the set of his potential romantic partners in the following way: a woman whom he finds physically attractive, with whom he shares interests, and with whom his personality is compatible. (That the woman is currently single is also important for many, including myself, but I recognize that it's less general than the former three, given the existence of polyamory/fidelity.)

However, for myself, I would add to this a fairly strict qualifier, that the woman is an atheist. I simply don't feel that I would be able to be emotionally intimate with a woman who holds an irrational, i.e. religious, worldview. Atheist doesn't necessarily mean rationalist, but religious almost definitely means irrational, i.e. P(rationalist|atheist) >> P(rationalist|religious), and even more so for P(would be open to rationality|atheist). I find it to be a sound heuristic that prevents me from embarking on relationships very likely doomed to failure. I doubt that I am alone among LWers in taking this into account.

Unfortunately, I have found it really damn hard to meet atheist women. I can count on one hand the number I have met in college. A large part of that is that I attend a science/engineering university which has a student body comprised of only ~30% women, but even then, my expectation before entering the university was that a population self-selected for interest in science/engineering would have a larger proportion of atheism than the general population. That expectation was not met by reality, and I recognized that I was confused, but trying to resolve that confusion (see below) didn't appreciably help my goal of meeting atheist women.

Studies have shown that women tend to be more religious than men. I also hypothesize that women who do select a science/engineering university are more likely to have gone to a private high school (76% of private schools are religious). As women tend to be socialized away from an interest in science, a stronger educational program than exists in the average public school might qualify as a "push" to counter that trend. I have met a fair number of women at this university who went to a religious school, but the sample size isn't large enough to confirm that hypothesis.

In any case, the problem remains: atheist women seem to be hard to find. The types of general activities you've suggested are good for socializing, but unlikely to have a larger-than-average atheist population. Are there activities similarly strong in socializing that would have a larger atheist population?

(Note: I don't mean to slight the obvious effort you put into this post; it's just that my own issues on this subject, and I suspect some others' issues as well, are more involved than just social awkwardness/inexperience.)

I'm confused as to what exactly you're asking here.

How do you buy a used car?

Another easy healthy thing:

Just about any vegetables can be boiled till soft, then put through the blender, salted and peppered to taste, and yield soup (cream is optional). A quartered peeled onion, half a bulb of peeled garlic, and a quartered peeled potato or two, plus a fair amount of peeled and roughly chopped whatever else (cauliflower, broccoli, carrots, parsnips, turnips, fennel, leeks, celery root or stalks, whatever) is a good template. Dump it all in a pot with water or stock. Boil till it'll smoosh against the side of the pot when pressed with a spoon. Blend. Salt & pepper.

"Programmers waste enormous amounts of time thinking about, or worrying about, the speed of noncritical parts of their programs, and these attempts at efficiency actually have a strong negative impact when debugging and maintenance are considered.
We should forget about small efficiencies, say about 97% of the time; premature optimization is the root of all evil."

--Donald Knuth (see also Amdahl's law)