Before you can cook bacalhau, you need to rehydrate and desalinate it by soaking it in cold water first. This not only removes some of the salt, but it increases the water content the fish as well (bacalhau gains around 35% more weight when soaked). 

HOW TO PREPARE SALTED COD

1. Cut the salted cod into large pieces
2. Run tap water over the bacalhau to remove any excess salt, before putting it in a bowl of water.  Soak the pieces of salted cod in a bowl of water
3. Cover the bowl with plastic wrap and store into the fridge. Skin side up. Why skin side up? The salt will sink as it is pulled into the water. If the skin was the other way around it would act as a barrier and salt would accumulate there instead of being pulled away.
4. Replace the water into the bowl every 4-8 hours. Make sure the bacalhau is completely covered in water.

5. After 16-24 hours, it should be ready. (NOTE: the saltiness of the cod and how many hours are necessary to soak the cod is not a perfect science each piece of cod is slightly different and it’s level of dehydration and it’s level of saltiness). If you’re not sure if it’s ready you could cut a small piece of salted cod and boil it for a 10 minutes, then taste to check if it is still too salty; continue soaking for an additional 8 to 12 hours. 

6. The Cod is ready to be cooked: Cook the cod at a gentle simmer from 10 to 20 minutes. In most recipes the cod is going to be cubed or shredded. Cook the cod until you could easily pull it apart with two forks. If the cod still seems to be salty at this time you could remove the cooking water and replace it with some fresh water bring to a boil for an additional 5 minutes. Save the water to boil the potatoes.

If you have a very large cod fillet, you can first cut it into 2 

After it has cooked, you can more easily remove the fish bones.

Loins: are thickest and flakiest section of bacalhau.  They can be roasted, baked, or grilled, and are ideal for bacalhau dishes that are not going to be cubed or shredded, but can be used on all bacalhau recipes

The other smaller pieces: are good for frying and shredding and work well in dishes like Bacalhau à Brás and Bacalhau com Natas. They can also be used in recipes that are shredded into fine pieces like Pataniscas de Bacalhau and Pastéis de Bacalhau. 

The tail): The tail is mainly used for adding flavour to recipes, it can be added to soups, stews, and rice dishes.