Any seafood that’s been previously frozen will be just as safe as any other food.

Get an instant read thermometer and your food will not only be safe but will taste great.

One trick is that ocean fish is safe to eat raw (assuming it has been kept refrigerated/frozen). If you have a cut of salmon or tuna, you can just sear it on the outside and serve it, no need to cook it all the way through (which will make it dry and tough). With saltwater fish, it's better to err on the side of less cooking.

Shellfish are more tricky, they need to either be raised and handled very carefully to keep them clean, or else cooked correctly. Oysters can be served raw, but you want to really trust the source and the handling.

Look up the timings and set an actual timer. Make sure your cookware is up to temperature before adding anything. Have enough experience to know how long everything else needs, so that you add your seafood at the right moment.

Scallops take very little time to cook, but a lot of seafood is more forgiving.

Also the danger of undercooking seafood is parasites rather than like salmonella. Good quality seafood is safe to eat raw - the stereotype of bad seafood giving you the shits is (as far as I understand) due to the ingredient itself being tainted.

Part of the art is that things keep cooking after you remove them from the heat, so remove them from the heat before they are done, so that they completely cooked when served.

Plate onto warm plates so they don't immediately suck all the heat out and the item goes cold.

Use a foil cover to keep heat in if needed.

Practice!