What not to do

Seven things that sink a project before the demo.

Deploy to mainnet.
Issue your own token if the product works without one. The judges see it on the first slide.
Write your own AMM, bridge, oracle or custody. It already exists, maintained and with public audits: Jupiter, Wormhole, Pyth, Switchboard, Squads. An audit reduces the risk, it does not remove it: verify the program ID per cluster.
Store personal data onchain. It is public and it does not get deleted.
Bolt blockchain on at the end, "to qualify for the track".
Leave the demo for the last minute. Record a backup video.
Use the public RPC for the demo.