What are some early signs that someone is faking or exaggerating a crisis to take advantage of me?

I ask for "early" signs because I usually don't find out until at least a year later, when the lent money is unreturned, or after I have exhausted so much time, energy, and resources in helping someone...or too deeply involved to get out quickly out of the relationship.

What are the early signs that the crisis someone is claiming is not legitimate or have been blown out of proportion?