Cards are more common to send and to receive. Americans usually give gifts to family and friends at Christmas, birthdays, weddings, graduations and child-births. Gifts are also sometimes given to someone who has moved into a new house or is moving away. Greeting cards are given to acquaintances who are not close friends. Gifts are not expected to be very expensive.
More expensive gifts are acceptable between people who are close to one another.
We usually give something which the recipient needs, wants or would enjoy. Americans usually open gifts in the presence of the giver. A verbal expression of thanks is appropriate. If the gift is opened in the absence of the giver, a thank-you note specifically mentioning the gift should be sent. This is an important custom for most Americans, signifying that you truly like the gift.