Index funds, generally. Ideally something more diversified than just an S&P500 one, but honestly historically it usually hasn't made _that_ much difference in the long run.
Assuming you're talking decades away, it usually all comes out in the wash.
Now, where you should really potentially worry is if you were retiring imminently and needed to pull out a bunch of money to make that happen. But if you're retiring in 20 years or whatever, and, say, the S&P halves next year, is it really, in the scheme of things, _that_ big a deal?
If you could time it perfectly, you could come out better by selling now and reinvesting after the crash, but bear in mind that you probably cannot time it perfectly. People were predicting the 2008 crash imminently from about 2004 on, say, whereas the dot-com crash went from dark mutterings to chaos in a year or so. These things are very hard to time.
Assuming you're talking decades away, it usually all comes out in the wash.
Now, where you should really potentially worry is if you were retiring imminently and needed to pull out a bunch of money to make that happen. But if you're retiring in 20 years or whatever, and, say, the S&P halves next year, is it really, in the scheme of things, _that_ big a deal?
If you could time it perfectly, you could come out better by selling now and reinvesting after the crash, but bear in mind that you probably cannot time it perfectly. People were predicting the 2008 crash imminently from about 2004 on, say, whereas the dot-com crash went from dark mutterings to chaos in a year or so. These things are very hard to time.