Whenever you are asked to give some suggestion, make sure the suggestion you give would not make them to question you back of whether you actually experienced it before.
The thing is, when people believe us so much and ask us suggestions, we should actually be very well aware of the problem they are facing currently, and it would be better if you answer only if you personally experienced it previously. Only then you will be able to understand the situation of the person in that particular problem. You will be able to recollect what have you done previously and thus suggest them with a best idea.
Without experiencing the situation, if you suggest, something, the consequences later have to be faced by you which might even lead to the break up of the relation between the both.