Make sure you have at least five high quality harpoons. A very large ship will be needed so make sure you have enough money. Many people make the mistake of hitting it in the tentacles, my advice would to hit its eye and smash its head to a pulp. Then spray salt over it and wait until its weak then grab a giant spoon and scoop its brains out through its eye socket. This will disable the giant squid which will enable you to shoot your five high quality harpoons and reel its carcass in.
The Giant Squid is perfect is perfect to feed to your guests at your birthday party.