Recently an interviewer asked me how I got to be such a good forecaster, and I replied by saying something humble. In retrospect it was a bad answer because I should have instead used the opportunity to give actual advice on how to forecast AI well. Here's a stream-of-consciousness attempt to do that:

1. The heuristic that things which sound weird and sci-fi are less likely to happen in reality, is bad. I suspect that's what really going on is that things which sound weird and sci-fi put you at risk of being judged a weirdo if you talk about them which is not the same thing as are unlikely to happen. Repeat to yourself the mantra that some weird sci-fi things really do happen, and others don't, and you have to take them on a case by case basis.
2. Trend extrapolation is your friend. Your best friend. Don't let anyone tell you otherwise. I've actually only rarely see someone extrapolate a trend too credulously; more often, people have a trend staring them in the face and extrapolate it a tiny bit into the future and then are too timid to keep extrapolating it. In general I think it's reasonable to extrapolate a trend as far into the future as it extends into the past. Now obviously, trend extrapolation is just the beginning of the forecasting process, it's not the end. For each trend you should ask yourself whether it makes sense for it to continue like that and if not why not etc. You'll usually end up with some sort of sophisticated view about how the trend will probably continue but bend downwards a bit and then ultimately plateau around X level.
3. Explicit models are also your friend. Things like Bio Anchors, the AI Futures Model, takeoffspeeds.com, etc. The process of making your own complicated model like this, and engaging with the models made by others, is... well, I think it's pretty edifying. I'm not sure why but I could speculate. Maybe something about teaching you to be appropriately humble (e.g. when the model output is sensitive to a parameter you have no clue about) and also teaching you to more quickly identify the considerations that matter most, and ignore the rest?
4. For short term predictions, especially about geopolitical events, the sorts of things that people are gambling about on Polymarket, the heuristic "nothing ever happens" is pretty good. Things do in fact happen, of course, but betting markets and online discourse tends to be biased a bit towards things being more likely to happen than they really are, and so you can get an easy win by just correcting a bit downwards from the 'wisdom' of the crowds.
5. Scenario forecasts are also your friend. They help you ask yourself the right questions, and they help you notice when some of the things you thought contradict each other.