Before you set off for the fishmonger's, there are a few key things to look for when purchasing shellfish. The trained eye can easily spot when a product is of superior freshness and quality – and so can you! To show you how it's done (plus serving and storing ideas), we've asked the experts from the renowned Sydney Fish Markets.

• Read our buyer's guide to shellfish

When buying any type of shellfish, look for:

• A pleasant, fresh sea smell
• No discolouration, gaping or bruising
• Bright, lustrous, firm flesh
• Any dark muscle should be pink-red in colour
• Brightly coloured, lustrous shells or flesh
• Shells that are closed (or close when tapped or gently squeezed)
• No discolouration, particularly at the joints

Crustaceans (eg prawns, crabs, rocklobster and bugs)

The shells of crustaceans turn bright red when cooked. If the meat has been removed from the shell, it is cooked when the flesh turns from translucent to opaque. The flesh is quite delicate and cooks quickly, so be careful not to overcook and toughen the meat. Barbecuing is a great way to cook crustaceans quickly and simply. Boiling or steaming is another way to ensure tender, delicate flesh.
Serve with: lemon, lime, onion, garlic, ginger, mayonnaise, tomatoes, basil, chillies, mint.
Storing: Consume as soon as possible after buying. Keep in a cool place with a damp cloth over the container.

Bivalves (eg vongole, mussels and pipis)

Bivalves are quick and easy to cook. You know when they’re ready because they open up. Before cooking, make sure each shell is either firmly closed or closes easily when gently tapped. Discard any that don’t. Simply cook in a pan over high heat with a little liquid, such as wine or water, and any other flavourings you like.
Serve with: lemon, lime, lemongrass, white wine, garlic, herbs, breadcrumbs, cream, curry spices, saffron, and tomatoes.
Storing: Consume as soon as possible. Place in a container, cover with a damp cloth and keep in the warmest part of the fridge, usually the crisper.

Molluscs (eg squid, calamari, octopus and cuttlefish)

Molluscs need either very quick cooking over a very high heat or very long, slow cooking over a very low heat, as anything else will make them tough. If cooking quickly, cook just until their translucent flesh turns opaque. Otherwise, braise gently until the flesh feels very tender.
Serve with balsamic vinegar, red wine vinegar, coriander, parsley, dill, fennel, mint, soy sauce, fish sauce, garlic, ginger, spring onions, tomatoes.
Storing: After cleaning and rinsing, place on a plate or tray, cover with a damp cloth and then with plastic wrap (or in a covered container). Store in the coldest part of the fridge and use within 2-3 days.

Tips for freezing

Meat from molluscs (such as squid and mussels) and crustaceans can be frozen for up to three months. Gut and clean squid, cuttlefish and octopus, or remove meat from shells. Place in an airtight freezer bag, extract as much air as possible, and be sure to label and date.

Place unpeeled prawns in a plastic container appropriate to the volume of prawns. Cover with water, seal and freeze. This forms a large ice block, which insulates the prawns. Do not add salt as this will draw out the moisture. Label, date and freeze.