I got a letter from one of my 5th cousins last week. I printed out what notes I had on my 3th great grand uncle John and his wife Sarah. I had a note that her [spinster] sister was Mary Mateer who died in Bridgeton (no parents names listed on death certificate). I checked Mary's will and sure enough, there were 2 cousins of mine that I didn't know existed. I also found that Susan Mateer Cornwell was, in fact, her sister. I then got a copy of Susan's death certificate listing only her father James Mateer. I checked the census and found he died between 1830 and 1850. Further digging found his wife was Susanna (Garrison) Joslin Mateer.
I photographed her tombstone in June of 2006 when I was photographing all the tombstones I could. She's buried next to her son Daniel Joslin in Friendship Finley Methodist Church in Deerfield, NJ. I don't know who her parents are as her death certificate didn't list them, but her full dates were on the stone as well as the correct spelling of Mateer.
Photograph everything you can digitally. It's cheap.