My favourite resource is Seafood Watch. They are an awesome group based out of the Monterey Bay Aquarium dedicated to finding a sustainable balance. Their website says "Scientists estimate that we have removed as much as 90 percent of the large predatory fish such as shark, swordfish and cod from the world's oceans. In 2003, the Pew Oceans Commission warned that the world's oceans are in a state of "silent collapse," threatening our food supply, marine economies, recreation and the natural legacy we leave our children." Wow, that blows. But there is something we can do! I always carry my handy regional pocket guide when going to the fish market. These guides put out by Seafood Watch, available for download or through an app, show what seafood is the best choice, what are good alternatives, and what should be avoided.
I'm in luck, here on the west coast squid is on the "good alternatives" list. Squid is generally considered to be very hard to over fish. They breed abundantly, have fairly short life cycles (approximately 9 months), and quickly adapt to changes in their environment. Here on the west coast we had a bumper crop of squid this year, so many that California ended its squid season 4 months early after fishers caught the maximum allowed weight.
I normally buy my squid pre-cleaned, just because it is less of a hassle. If you want to go for it with whole ones, cleaning them is a fairly straightforward process. If you are used to cleaning fish this probably won't gross you out - if you aren't you might want to get the pre-cleaned ones because this is going to be messy. Instead of explaining the whole process here I am just going to give you guys this link. Good luck!
The key to cooking tender delicious squid instead of gummy, bland, rubber band squid is timing. You either have to cook squid very briefly, for under 2 minutes, or, if you pass that thresh hold and it gets gummy, you have to cook it for over 30 minutes to re-tenderize it. Some dishes call for a long cooking time, but for the marinated squid salad I made all you have to do is slice the heads and parboil it. Drop the pieces of squid in boiling water, leaving them in just until they turn opaque, about a minute. When you take them out of the boiling water, put them immediately into ice-water, or run cold water over them to stop the cooking process. If you don't do this the squid will keep cooking and very quickly turn into rubber bands.