His wife was Jewish, and occasionally attended TBI. One thing he and I have corresponded about was Jewish mourning customs. It seemed responsible to share with him a "heads up" about how his wife's Jewish friends will typically express condolences--and to then share my comments here in case they can be of help to others as well.
Most of Jewish grieving traditions are based around community, in three ways, although there are of course also traditions about what happens at a Jewish memorial service. These traditions are helpful and good things, but they can take someone not used to them by surprise.
First, the community cares for the family in mourning so that the family can focus on mourning. This is traditionally done for an entire week. As a mourner, don't be surprised if Jewish friends offer to bring you prepared meals, to babysit, to clean your house or do yard work, or in other ways try to do the tasks of day-to-day life for you with the purpose in mind of allowing you to focus on mourning. In some cities it is even traditional for a person to stay at the family's home to answer the phone, so family members need not do so.
Second, everyone gathers to share stories that highlight the virtues of the person who died, to inspire everyone present to better practice those virtues and in doing so honor the deceased with their lives. This is traditionally done at the family's home after the memorial service, but sometimes happens at the memorial service. If no time is set aside for sharing stories as a group then Jewish friends will likely try to share their stories one-on-one. As a mourner, if you don't want Jewish friends to start conversations with you by their describing what they admired about the deceased (as spotlighted by an anecdote or two) you may have to explicitly say so. If you have young children who would not remember or understand the stories, you might want to redirect this Jewish habit into contributions of written stories which can be valued by these children in future years.
Third, Jewish people traditionally donate money to a charity that the deceased supported rather than buying flowers. As a mourner, don't be surprised if Jewish friends don't send flowers, or if they ask to where they can donate money in honor of the deceased and his or her values.