How safe and effective is using a deck of angel cards to obtain inspiration and guidance?

Just because one is using a deck of angel cards does not confer protection of any kind. You are not automatically safe in a church simply because it is a church. You must be in divine alignment, and if you want protection, must request it. So the same rules apply, that any kind of procedure desiring intuitive feedback should begin with a request to the divine for protection as well as guidance to achieve what is highest and best, and ideally by individuals who have worked to cultivate their faith, so they have a high belief quotient in the divine, as well as belief in themselves as worthy and deserving of divine partnership. Relatively few people can meet these criteria and is often the reason why they are consorting with such tools to begin with. They feel something is missing in their lives and want to fill the gaps and use such a device as a means of reassurance, thinking the cards will allow a communication that otherwise would be impossible. In a sense, that might be true if there is meaning to what is presented by the cards which is interpretable by the individual, and that can indeed be arranged through divine means to provide a message that is very much needed and desired. But all too often, such practices are a kind of crutch that is intended to bridge a gap that the individual fears exists. So they need some kind of adjunct to obtain information and guidance when that is truly not the case. The same intuitive sense they will use to interpret a card reading, they can generate directly from their intuitive sensing, without a prop of some kind that may, in the wrong hands, actually introduce confusion, and obfuscation, and greater inaccuracy.