Genesis 24: Looking for a sign from God

Gen 24:11-15

He made the camels kneel down outside the city by the well of water; it was toward evening, the time when women go out to draw water. And he said, “O LORD, God of my master Abraham, please grant me success today and show steadfast love to my master Abraham. I am standing here by the spring of water, and the daughters of the townspeople are coming out to draw water. Let the girl to whom I shall say, ‘Please offer your jar that I may drink,’ and who shall say, ‘Drink, and I will water your camels’—let her be the one whom you have appointed for your servant Isaac. By this I shall know that you have shown steadfast love to my master.”
Before he had finished speaking, there was Rebekah, who was born to Bethuel son of Milcah, the wife of Nahor, Abraham’s brother, coming out with her water jar on her shoulder.

Why don't my prayers for a sign ever get answered? Why do some people see signs everywhere when they are no signs at all?

Part of the answer may have to do with the fact that, in this case, God was interested in who Isaac married and (as the servant mentioned in his prayer) God was invested in the long term vocation of Abraham's seed.

It is noteworthy that God did answer the servant's prayer but not in the way it appears on the surface of the text.

The servant's prayer asks for God to chose the girl who responds in a particular way to a request for a drink. The prayer does not ask for the girl chosen by God to respond in a certain way to a request for a drink.

When Rebekah responds in the prescribed way, the servant hopes God will choose her. Evidently, through some prophetic means, the servant is able to determine that Rebekah is indeed the girl for Isaac (Genesis 24:21).

Genesis 24:67

Then Isaac brought her into his mother Sarah’s tent. He took Rebekah, and she became his wife; and he loved her. So Isaac was comforted after his mother’s death.

Notice the order of the events that sealed the union of Isaac and Rebekah. Isaac

(1) took her to bed,
(2) "took her" as his wife,
(3) loved her.

The order is a nice order and actually the typical order even in western marriages. In the "dating" phase, couples typically believe they are in love; but successful marriages include a period of growing in love which is more lasting than the emotional high that dating couples feel. Isaac experienced the same marital love that all Christian marriages should pursue.