There is no need to visit the chapel of rest, though if you are a member of the family or a close friend you may want to. Equally, unless you are a family member or close friend you should make your own way to the ceremony.
In some cases, particularly for Roman Catholic funerals, the coffin may have been in the church overnight, but normally it is brought in after the mourners have gathered. In the latter case, mourners should enter the church before the coffin and stand when it arrives.
At a crematorium it is more normal for mourners to wait outside and follow the coffin and family members into the building. Whether the ceremony is held in a church or a crematorium, the seats at the front will normally be reserved for the chief mourners. Fill in the seats behind them, rather than sitting at the back: it makes the family and friends feel more supported, and any singing will be more confident and cheering.
At the end of the ceremony the chief mourners should be allowed to leave the building before everyone else. Often they will stand near the exit to shake hands with the departing guests, in which case you can say a few words or just smile and move on.
If there is a church service followed by a burial at another site, and you are invited to both, you should follow the hearse and the family cars from the church. Often, however, only family and close friends attend the burial; if that is the case other friends usually wait wherever the wake or funeral tea is being held, for the family to return from the burial.
Some churches and most crematoria have toilets you can use. Churches are less likely to have baby-changing or disabled facilities, though these will normally be available in the church hall (if it’s open) if the church lacks them.
If you are considering taking babies or small children to the ceremony, ask yourself first whether they are likely to disrupt the proceedings. While some mourners may welcome the sound of young life, others could find it upsetting. Older children may want an explanation of what’s happening and what death is; you can find some answers here.
If you knew the deceased but not their family and would like to attend the funeral, you may, unless it is specifically for family only. The relatives will be pleased to meet you and learn of your relationship with the deceased, and to know that you cared enough to want to attend.