To answer this question, I would like to divide the issues into two categories: responsibilities to the deceased and responsibilities to the living.
Insofar as paying respects to the deceased, it used to be that everyone in a town went to everyone’s funeral (Shulḥan Arukh YD 361). However, this was the rule for small village communities. Nowadays, one would only be required to attend a funeral if not attending would be an embarrassment to the deceased. Usually, this would be because one is such a close friend or relative that he or she would be expected. It could also be because so few people in general are attending the funeral that everyone who can attend should; sparse attendance may imply that the deceased was not important or well-liked.
Since you did not know the deceased, assuming you have no reason to believe that the funeral will be drastically under-attended – and it is not your responsibility to ask, as this is unusual – you do not need to attend the funeral to honor the deceased.
Insofar as honoring the living, this can be done in a number of ways. Although certainly your friend or co-worker will appreciate your showing up to his or her loved-one’s funeral, this is generally not expected. Additionally, mourners are often emotionally preoccupied during funerals, as they should be, and the appearance of acquaintances is a secondary or tertiary issue in their minds, if they notice it at all.
The main way in Jewish law and practice to show sympathy and solidarity with the mourner is during the shiva period (Shulḥan Arukh YD 376). During this period, the mourner sits in his or her house and receives comfort from visitors. If your friend or co-worker will be sitting shiva, and you feel that it would not be awkward or inappropriate to make a shiva-call, this would be my first suggestion. Shiva is a time for mourners to express their feelings about their loved one or about their loss or other related subjects on their mind.
If the person will not be sitting shiva, I would even suggest that you offer to sit with them, perhaps over a cup of coffee, and talk, mimicking the shiva experience in some way and allowing them to reflect on their lost loved one. However, if you feel that this would be awkward or inappropriate, or somehow not in keeping with the nature of your relationship with this person, then I would suggest either offering them your condolences with a card, or an email, or even a small charitable donation in the deceased’s honor.
I hope this answer was helpful to you,
Zev Farber
Answered by: Rabbi Zev Farber