1- typing "Unknown" in a space meant for a family name. If you don't know it, leave it blank or it will show up when accepting information from resources such as family trees! (Ancestry.com)
2- typing the dates the wrong way. The proper way to write the dates is to write it out. 3 June 1970 is how it must be written out on Familysearch. Why not do this on every site? I have also seen it done this way 1970-00-00 if only the year is known. Please don't do that. Just put the year. If you don't know the date at all, leave it blank.
3- If you do not know the wife's name, do not replace it with her married name. Leave it blank. It will mess up the matching process and you will get a lot of resources that do not apply to the woman. If you don't know the woman's name at all, please leave it blank. Do not put things like "Mrs. Berry" or "Mrs. William Berry". Leave it empty. If I accept your family tree I do not want to have to correct everything. I have begun to not accept family trees with these mistakes in them. (Ancestry.com)
4- Listing just the name and nothing else. If you know an approximate date, list it. If you know what country, at least list the country. If you know the state, add that and so on. I usually estimate at least 20 years younger than the first child's birthday when trying to figure out the mother's birthdate.
5- When you accept sources, make sure the dates and places match the information you already have. Make sure you do not list a child to a family where the child is born around the same time as the mother. Make sure the women are not too old to have children. I usually get wary when the mother is in her 50s and still having children, but it happens.
6- Make sure that you give a gap of at least 9 months between children, unless they are listed as twins. You should not have multiple children born in one year with different birthdates unless the first is born in March and the second is born in December, and even that is unlikely.
7- I don't know who does it, but when putting where a person was born or died, please don't put "ENG/MASS". If you do not know if they were born in England or Massachusetts, leave it blank.
8- I don't know who does that, but I think there is only one person who does this and it really annoys me: don't put "5-s & 3-d" in the section that asks you to list out the children. They want their names. If you must do something, put "Baby boy" 5 times and then enter the last name. Then add "Baby girl" 3 times and add the last name.
9- Familysearch- There is a number of misinformation in the trees, and often it will not allow you to delete or merge the person to correct it. VERY FRUSTRATING!
10- Type capitol letters on the beginning of all names unless it's nationality calls for a lowercase letter (such as with a surname like: "van Otterloo".)
11- I love when the address of where a person died is added to the "place of death" for people from the UK area. However, there is only room for a town, county, state and country. Please add that note elsewhere on the person's profile.
12- Findagrave.com users- IF you do not know where a person is buried and do not know where the memorial is, please do not create an account for that person. This site is called "Find a grave" yes, but you have to find the grave first in order to post it. At least know what cemetery they are in.
14- A note to let people know that not all vital records are correct. Example in my own tree: The marriage of my great Grandmother and Great Grandfather, my Gr. Grandmother actually lists her grandmother as her mother. I don't know if she was aware of that error or if she really didn't know her mother's name, but even though I have the record of their marriage, and it is recorded in the vitals that way does not make it correct.
15- Native American ancestors- There are a lot of tales and family legends that include Native Americans in otherwise white (or other nationality) families. Some may be correct. Some may have a bit of truth to them, and some may be totally made up. If you can back up your random Native American with something other than someone else's family tree, records somewhere, diary entries, skills etc. at that as a source. Check out if the date and place your ancestor is said to have lived matches what was going on in that time period. Don't expect Anglo names from your Native relatives, but don't expect that they did not also have an English name given to them by the white people so that they could remember and pronounce their name. Back in the 1600s, the English language did not have correct spellings of much of anything. Thus, mutations of names and places have occurred over the centuries. This goes for Native American names and places as well. Names will have odd spellings because they would spell the name how it sounded to them. "No- Pee" derived from "Nope". It is not necessarily a hoax, but make sure all the dates and places match before even accepting the information.
-- be aware of mentions of "Indian princesses" in your family tree.
-- Learn about what tribes were in that area around the time your ancestor was and see if it matches facts.
-- Know that if the marriage was a tribal marriage, there may be no record of the wedding.
-- Make sure your sources are credible.
16- Often if a baby was born and died young or if a child was born and was deemed "simple" or any other words to describe a defect, the parents may name another child with the same name. Make sure you don't merge these children together. Get rid of duplicate names in your family tree (if the program lets you like Familysearch who may not).
17- If a death certificate lists a cause of death, take note of that in that person's profile. It is an interesting way to track the health of a family over the generations.
18- Many people used to use the same names generation to generation. I get why, but it really makes finding the right people really difficult. That is why other information is so important, so you can tell one Elizabeth Smith from the next ten Elizabeth Smiths in the tree.
19- Please READ CAREFULLY the information you accept into your tree! Other people doing their trees what the facts of their ancestors. Do not blindly accept any and all information you find. If you are not sure, save that information elsewhere until you find out that it is a match. This goes for Familysearch and Ancestry (those are the two I work with). If you cannot find a person in one of these family tree sites, try Googling the ancestor and finding the information elsewhere. You may be surprised at what you find out!
20- I've notices that some sources that pop up as hints have very little information to them to the point where it could be my person or maybe not. There are census records that just has a list of men on them. No other information. There is no way I can tell if that person with the same name is my person from that census. I won't accept those types of hints.