I have been mushroom picking ever since I was a kid, and there are a number of key rules to follow if you want to stay safe.

Firstly, pick ONLY the mushrooms that you're absolutely 100% sure you are familiar with (start small, gain experience), and this can be done by ignoring all mushrooms types you're even a slightly bit unsure about. Another helpful rule we follow when picking, is by checking under the cap, and if it's spongy and not harmonica shaped you are generally picking an edible mushroom... there are of course delicious exceptions like chanterelles and or pine mushrooms that grow all over BC, but I would say those should be picked by more experienced mushroom hunters that know the little minute details as mushrooms have a tendency to look similar yet slightly different. i.e death cap and pine mushroom.

Also, if you're unsure of a mushroom, you can pick it, and cut the cap in half to check for bugs. Most edible mushrooms will have signs of burrow holes made by bugs eating them. You will not see these same signs of edibility on poisonous mushrooms, having said that obviously many edible mushrooms can be bug free (young, good location, healthy, etc), and you should be discarding those that are infested, but it's good experience to just check and learn as you get to know the mushroom kingdom.

The last thing, and I think it's the most important. After a "mushroom hunt", always have an experienced mushroom hunter around to help you clean and prep the mushrooms. They will easily spot any poisonous ones out of the pile and point them out to you so you can learn for next time.