Don't transfer 401(k)s, IRAs, or HSAs directly into a trust. The custodian treats it as a distribution and you'll owe income tax on the full balance. Instead, name the trust as beneficiary to keep the tax deferral and control how heirs get the money.
Unless you enjoy dealing with the IRS, do not put these things in your trust. Your 401, your IRA, tax-deferred annuities, health savings accounts, medical savings accounts. If you transfer any of these types of accounts to your trust, the IRA will treat them as distributions and you'll have to pay tax on the entire amount. Instead, make the trust the beneficiary of all those accounts. Then you control the way those accounts are distributed to your heirs and you could make it so that they're protected from creditors. Follow me for more wiseness.