I've done quite a few.
- Make sure the immediate family actually wants you there, not just some extended family relative.
- Dress the part
- If you have to use flash, use it before the service actually starts. I never use it during the actual service.
- Use a wide angle to get a view of the people there, to document the event. (Front to back, vice versa)
- Use a long lens to get groups of family and friends sitting together. (Funerals and Weddings are the only two events that out of town relatives really get together)
- Try NOT to get someone in extreme grief.
- If you must move around, during before the eulogy.
- If there are going to be speakers, or a solist, find a perch to get one or two shots of them.
Many funerals, (at least in my experience) are more of a celebration of life, rather than the grief striken types you see on tv, so some can be quite festive events, lots of singing, music, (funny) storytelling. Depends on the family. If its an older person who has been ill, most are ready, in a sense, or have prepared for their passing. Kids and tragic accidents are the worse.
Its not much different than a wedding, you just try to be invisible and less of a distraction. Capture the event.
The same rules apply if you're asked to go to the cemetery.
If there is Repast, you may be asked take photos of individuals and groups of family who havent seen each other in a while.