Give your executor your bank/broker's signon and password.
Assign transfer on death while living to every non-retirement account. Takes precedence over PoA, no probate.
Assign a PoA to the retirement accounts, if you're incapacitated and someone needs access to the money to care for you it is extremely hard to do if you're not lucid. That PoA expires the moment you die.
Have a will, state your burial preferences in it as kids may fight over how to dispose of you.
You'll need a Letter of Testamentary or Muniment of Title to convert some accounts, that requires a lawyer.
Different counties/states have different rules, my house in Weatherford was in joint name, my wife died and to get her name off the deed Parker County required me to probate the will. That cost about $3000.
10 copies of the Death Certificate are more than enough.
Don't pay any bills with your money, if the deceased has bills the estate can pay them, if there's no money and the deceased has none let the creditor sue the estate. Most won't. But if the estate has bills and the beneficiaries get money and the estate hasn't paid bills the beneficiary may get sued. FWIW USAA has a great estate section and they are great with advice.
So to summarize when my wife died it took a trip to my broker to change titling on all of our accounts (my broker is also my banker, Merrill Lynch), a letter to the state to change the car titles, a trip to the county courthouse to schedule a probate hearing and another trip to actually attend the hearing, The hardest part was setting up a service because we didn't have a church and even though wife didn't want a service the kids did and a LOT of people showed up. I also re-did all my wills and hospital directives, another $1500 or so,