This is kind of morbid, but I want to give some tips on how to act and react at a Shiva. There are already a number of places online with some good tips, but I’m going to try to boil it down to some essentials.

1. It’s not about you.

This is the most important thing to remember. You’re going to be uncomfortable. It’s an awkward and agonizing experience for the mourners and for people trying to comfort them. Get over yourself. Try to be open and helpful, but shut up and/or leave if you get the urge to talk about yourself or your own loss.
It Will Suck: Do It Anyway

2. Put down the bouquet.

Flowers aren’t Jewish. I have been to a number of shiva houses where nice bouquets sit in the middle of the dining room table, and everyone passing by comments on how tacky they are. I don’t think they’re tacky, but they’re not a part of Jewish mourning. If you feel the need to bring something, see number 3.

3. Bring (appropriate) food.

Often communities coordinate things in order to stock the freezer of the home of the deceased. Bringing food to a shiva is generally a good idea, BUT keep in mind the family’s level of kashrut. If you’re not positive that they’d eat in your house then don’t bring anything. I have seen people throw out tons of food because it wasn’t up to their standards or kashrut. It may seem annoying, to you, but then, it’s not about you.

Sometimes a family will say, “Hey, we can’t take any more food.” If that’s the case, ask if you can bring a meal for them in a few weeks, when things have died down a little. In some cases meals will be coordinated by the community for more than a month after the shiva. Be prepared to wait to make your contribution.

4. You don’t have to wear black, but cover up.

Jews don’t have a color of mourning. Many people do wear black, but it’s way more important to dress respectfully. Do not show cleavage. Do not unbutton the top three buttons so the ladies can see your fine chest hair.

5. Don’t try to lighten things up.

When approaching a mourner you don’t greet them, and they don’t greet you unless they want to. They may want to chat, but if it’s been a busy day, often they don’t want to talk anymore. Don’t babble, don’t make jokes, and don’t try to distract them from their pain. Make yourself available as a listener, and then just sit quietly.

6. Bring Art

If you have any great pictures of the deceased make copies and bring them for the family. Often a display will be set out. Showing the mourners the pictures can be a good way to start a conversation about good times with the deceased. Don’t push it, but offer the pictures as a gateway.

7. Don’t bug them to eat or drink.

That’s Great Aunt Elma’s job. Nagging at shiva is the height of insensitivity.

8. Make a donation.

Most families will have designated a few charities that they’d like to have money sent to in lieu of flowers. If you can afford it, this is a meaningful thing to do.

9. Write a note.

“I’m so sorry for your loss” is fine if you can’t think of anything else to say, but if possible it’s best to share an anecdote about the person who has died. Buy a card, and send it in the mail with a stamp and everything. Families often save these notes, which is why e-mail is not ideal.

10. Make an appearance.

Even if it feels excruciatingly awkward, you should go. Even if you can’t think of anything at all to say, and you don’t even think you’ll get a chance to talk to the family, you should go. Someone will notice that you’re there.

(I once went to the shiva for a son of a rabbi in my community. I went for davening, but didn’t stay for the meal afterwards, and didn’t get to talk to the rabbi or anyone in the family. I didn’t think anyone saw me, but six months later in the middle of a conversation about something else entirely the rabbi told me how much he appreciated seeing me there.) Go, even if it’s only for five minutes.

11. It’s not about you.

Seriously.