Let's say that you are invited to the party of an American friend: a birthday party, wedding, baby shower, bar/bat mitzvah, or some other type of special occasion. Unless otherwise stated by the host, it is usually expected that you should bring a gift to the party. So let me offer you some advice on this!
Birthday party: The gift that you bring depends on the person the party is for. (Is it for a 10 year old boy or a 25 year old woman?) It is okay to ask for gift ideas from the person. Money or gift cards are acceptable gifts to bring to a birthday party.
Wedding: Most couples have a wedding registry at a store. The registry will include items that the couple needs for their new home/life together. Ask the couple which store they are registered at so you know what they need. It is okay to buy something that is not on the registry, but most couples are very pleased when items from their registry are purchased. Also, it's very important to know that if you buy something from a registry, you need to let the store know.
Baby Shower: As with weddings, most parents will create a baby registry at a particular store. If not, then typical items purchased for a baby shower include: baby clothes, diapers, baby toys, baby soap/shampoo, etc. If you are uncertain of the gender of the baby, make sure you buy gender-neutral colors, such as green or yellow.
Bar/Bat Mitzvah: As with most adolescents, money is a popular gift to give at a bar or bat mizvah. In the Jewish religion, the number 18 is very significant, so giving an amount of money that is a multiple of 18 would be meaningful. Also, gift cards to the young person's favorite restaurant or store are acceptable as well.