It feels to me that rationalist principles are most useful in avoiding failure modes. But they're much less useful in coming up with new things you should do (as opposed to specifying things you shouldn't do).

I'd start by asking whether the unknowns of the problem are primarily social and psychological, or whether they include things that the human intuition doesn't handle well (like large numbers).

If it's the former, then good news! This is basically the sort of problem your frontal cortex is optimized to solve. In fact, you probably unconsciously know what the best choice is already, and you might be feeling conflicted so as to preserve your conscious image of yourself (since you'll probably have to trade off conscious values in such a choice, which we're never happy to do).

In such a case, you can speed up the process substantially by finding some way of "letting the choice be made for you" and thus absolving you of so much responsibility. I actually like to flip a coin when I've thought for a while and am feeling conflicted. If I like the way it lands, then I do that. If I don't like the way it lands, well, I have my answer then, and in that case I can just disobey the coin!

(I've realized that one element of the historical success of divination, astrology, and all other vague soothsaying is that the seeker can interpret a vague omen as telling them what they wanted to hear— thus giving divine sanction to it, and removing any human responsibility. By thus revealing one's wants and giving one permission to seek them, these superstitions may have actually helped people make better decisions throughout history! That doesn't mean it needs the superstitious bits in order to work, though.)

If it's the latter case, though, you probably need good specific advice from a rational friend. Actually, that practically never hurts.

A few principles that can help in such cases (major decision, very little direct data):

• Outside view. You're probably more similar to other people than you like to think. What has worked for them?
• Far vs Near mode: beware of generalizations when visualizing distant (more than a few weeks!) results of a choice. Consider what daily activities will be like.
• Avoiding oversimplified modeling: With the exceptions of procreation and suicide, there are almost no life decisions that are permanent and unchangeable.
• Shut up and multiply, even for yourself: Many times it turns out that minor-but-frequent issues dominate your happiness. Weight your pros/cons for future choices based on this, not just on how important something "should" be.

...I don't suppose you can tell us what? I expect that if you could, you would have said, but thought I'd ask. It's difficult to work with this little.

I could toss around advices like "A lot of Major Life Decisions consist of deciding which of two high standards you should hold yourself to" but it's just a shot in the dark at this point.

One problem is that I just don't have enough "evidence" to make meaningful probability estimates. Another is that I'm only weakly aware of my own utility function.

Based on those two lucid observations, I'd say you're doing well so far.

There are some principles I used to weigh major life decisions. I'm not sure they are "rationalist" principles; I don't much care. They've turned out well for me.

Here's one of them: "having one option is called a trap; having two options is a dilemma; three or more is truly a choice". Think about the terms of your decision and generate as many different options as you can. Not necessarily a list of final choices, but rather a list of candidate choices, or even of choice-components.

If you could wave a magic wand and have whatever you wanted, what would be at the top of your list? (This is a mind-trick to improve awareness of your desires, or "utility function" if you want to use that term.) What options, irrespective of their downsides, give you those results?

Given a more complete list you can use the good old Benjamin Franklin method of listing pros and cons of each choice. Often this first step of option generation turns out sufficient to get you unstuck anyway.

I am not that far in the sequences, but these are posts I would expect to come into play during Major Life Decisions. These are ordered by my perceived relevance and accompanied with a cool quote. (The quotes are not replacements for the whole article, however. If the connection isn't obvious feel free to skim the article again.)

To do better, ask yourself straight out: If I saw that there was a superior alternative to my current policy, would I be glad in the depths of my heart, or would I feel a tiny flash of reluctance before I let go? If the answers are "no" and "yes", beware that you may not have searched for a Third Alternative. ~ The Third Alternative

The moral is that the decision to terminate a search procedure (temporarily or permanently) is, like the search procedure itself, subject to bias and hidden motives. You should suspect motivated stopping when you close off search, after coming to a comfortable conclusion, and yet there's a lot of fast cheap evidence you haven't gathered yet - Web sites you could visit, counter-counter arguments you could consider, or you haven't closed your eyes for five minutes by the clock trying to think of a better option. You should suspect motivated continuation when some evidence is leaning in a way you don't like, but you decide that more evidence is needed - expensive evidence that you know you can't gather anytime soon, as opposed to something you're going to look up on Google in 30 minutes - before you'll have to do anything uncomfortable. ~ Motivated Stopping and Continuation

I suspect that a more powerful (and more difficult) method is to hold off on thinking of an answer. To suspend, draw out, that tiny moment when we can't yet guess what our answer will be; thus giving our intelligence a longer time in which to act. ~ Hold Off On Proposing Solutions

"Rationality" is the forward flow that gathers evidence, weighs it, and outputs a conclusion. [...] "Rationalization" is a backward flow from conclusion to selected evidence.
~ Rationalization

Your effectiveness as a rationalist is determined by whichever algorithm actually writes the bottom line of your thoughts. If your car makes metallic squealing noises when you brake, and you aren't willing to face up to the financial cost of getting your brakes replaced, you can decide to look for reasons why your car might not need fixing. ~ The Bottom Line

Hope that helps.

Just remembered: I managed not to be stupid on one or two times by asking whether, not why.

I just came out of a tough Major Life Situation myself. The rationality 'tools' I used were mostly directed at forcing myself to be honest with myself, confronting the facts, not privileging certain decisions over others, recognizing when I was becoming emotional (and more importantly recognizing when my emotions were affecting my judgement), tracking my preferred choice over time and noticing correlations with my mood and pertinent events.

Overall, less like decision theory and more like a science: trying to cut away confounding factors to discover my true desire. Of course, sometimes knowing your desires isn't sufficient to take action, but I find that for many personal choices it is (or at least is enough to reduce the decision theory component to something much more manageable).

The dissolving the question mindset has actually served me pretty well as a TA - just bearing in mind the principle that you should determine what led to this particular confused bottom line is useful in correcting it afterwards.