As a tester, I learned the standard test techniques of boundary conditions, equivalence classes, state models, path analysis but I’m always on the look-out for new test ideas, how things can go wrong and the ways that people can use things that were never thought of.
One source of this is The Risks Digest, which has been reporting on risks and problems since 1985. Some of the problems reported on are big ones such as Heartbleed, but there are a lot of smaller, less-publicized ones. For example Mazda had to recall cars because of petrol-sniffing spiders. While you may not have to worry about spiders, this story can trigger test ideas. Are there other users who might want to get hold of the data in your app? Is there something or some way that users can get themselves restricted?
Have you thought about all the user scenarios? What if your audience likes to surf (not the Internet, but actual surfing at the beach)? What do they do with their Smart Keys? Leaving them in the car unlocks the door, and they can’t take the keys with them, as the keys are not waterproof. Is this a minor edge case not worth worrying about? Asking the question can find out whether it is worth consideration — and could also bring up other scenarios not considered.
Users have many needs and can use things in ways that you never thought of. Getting exposure to a wide range of experiences and learning from other peoples mistakes can help you avoid these same traps. Places such as Risk Digest are a good way to find out some. If you can recommend any other resources, then please let me know in the comments.