3
Check the deadline, then take your time
You usually have months. Use some of them.
Claim deadlines for large jackpots are typically between 90 days and a year depending on the state and the game. Find yours — it is on the lottery's website — and write the date down.
Then do not rush. Winners who claimed within days are consistently the ones with a second news story attached. Winners who took two months to assemble a team before walking in are consistently the ones you never hear about again.
The exception is the annuity-versus-cash election, which in some states must be made within 60 days of claiming and is irrevocable. That deadline can be much shorter than the claim deadline. Check both.
There is one thing worth doing immediately, though, and it costs nothing: put the ticket somewhere that survives a house fire and a burglary. A bank safe deposit box is the standard answer. A photograph of it in cloud storage is not a substitute, but it is better than nothing while you arrange one.