When the woman saw that the fruit of the tree was good for food and pleasing to the eye, and also desirable for gaining wisdom, she took some and ate it. She also gave some to her husband, who was with her, and he ate it. (Gen. 3:6 NIV)
I've always found the reasons for Eve's tasting of the forbidden fruit interesting, since I think they cover the gamut very well. There are some things that tempt by immediate appearance, hence, pleasing to the eye. But most temptation is by signs, which are ultimately established either by its inferable causal associations (hence, good for food) or by what others tell us (hence, desirable for gaining wisdom). When Eve is tempted, she can see immediately that the fruit is pleasing to the eye, but she hasn't eaten of it yet, so she doesn't actually know that the fruit is good for food; all she has to go on is how the fruit looks, and on the basis of this she takes it to look like fruit that is good for food. And the only reason she thinks of the fruit as desirable for wisdom at all is because the serpent told her that it was.
This seems quite general. People are tempted because sin has an immediately pleasing appearance, or because they take sin to be useful for something, or because they have been taught by someone that it is really good.
These, then, are the three arenas in which temptation typically takes place:
(1) what is immediately desirable
(2) something's being a sign for something desirable
(3) signs that tell us that something is desirable
Since temptation is how one goes wrong, these are the areas of life in which prudence is especially necessary. Aristotle recognizes this for (1); one of his major pieces of practical advice is that we should be especially careful in all matters in which pleasure is intimately involved, because we are inclined to favor what pleases regardless of whether it is actually good. Plato certainly recognizes some of the issues with (2) or (3).
The first arena, that of the immediately pleasing, is, I think, a relatively small one. We are sometimes tempted by mere 'delight to the eye', but this is not common. We are far more tempted by what we take things to be signs of, and what signs (like the testimony of others) tell us. This of course is not surprising: temptation always involves treating good as bad or treating bad as good, so there generally has to be some sort of obfuscation going on to make things seem topsy-turvy enough to tempt us. And nothing has so much power to lead our minds astray like signs. Signs exert a causality on us, an external formal causality (the technical term is 'objective causality'); they present us with objects that specify how we think. So when our thinking goes wrong, distortion of signs or distortion by signs is often at the root.