Most giveaway complaints are not about who won. They are about whether the draw could have been fixed. A fair draw answers that before anyone asks.
Step 1: lock the list (commit)
Before the spin, the list of entries is fixed and a fingerprint of it is published, together with a sealed fingerprint of a secret number. Nobody, including you, can change the list or the secret afterwards without the fingerprints changing.
Step 2: spin
The winner comes from the secret and the list together. You spin live, exactly as you would with any wheel.
Step 3: reveal
After the spin, the secret is published. Anyone can feed the list and the secret into the same calculation and get the same winner. If anything had been changed, the fingerprints would not match.
Checklist before you announce
- Publish your entry rules and the closing time.
- Remove duplicate and invalid entries before you lock the list.
- Share the proof link together with the winner.
- Keep the entries file in case someone asks for it.