The most important consideration is whether you're giving advice "as" something special. An example would be claiming to be a medical doctor and advising people to do something clearly harmful such as "take 10 Tylenol and call me next week". In such an extreme case, there could be criminal charges. Less severe would be an accountant giving grossly wrong and incompetent tax advice to a client, in which case the accountant could be civilly liable. (For instance, telling a client "you don't have to declare royalties for textbook sales"). In such cases, a client depends on the professional to give competent advice, and you rely on him to work according to a certain professional standard of care. There is a difference between the standard of care that an ordinary "reasonable person" owes to any other person, and the standard of care owed by a professional in an area. What would be excusable bad advice that I might give on how to build a wall would be inexcusable if given by an engineer.
The basic idea is that if you interact with a person (even indirectly, manufacturing something that a 3rd party buys), you have a certain duty to be cautious. If this is just an ordinary-person on ordinary-person interaction, then the parties (both parties) are expected to exhibit the degree of caution that a "reasonable person" would exhibit (attempts to pin down what a "reasonable person" would do have proven impossible, though juries always know subjectively what a reasonable person would do). However, your duty to not give bad advice is offset by the advice-taker's duty to not take bad advice – that is, if a reasonable person would know that taking 10 Tylenol is a bad idea (thus I, as a non-physician might have some duty to not give such stupid advice), then the person who stupidly took 10 Tylenol was contributorily negligent in taking the 10 Tylenol.
As far as I can tell, if you do not represent yourself as a member of a technical guild (lawyer, doctor, accountant, many others) giving technical advice in that capacity, and you are not directly contracting with a person (i.e. they hire you to give them advice on how to keep your yard from falling over the cliff), then you can say stuff like "If X, then you should Y", and not have to pay if someone does that Y and they suffer a loss.