Most of the list of data formatting errors in spreadsheets is from the Data Carpentry lesson, Data Organization in Spreadsheets.
Many people use spreadsheets in their research and work. A pitfall, especially when trying to create reproducible research, is trying to make the spreadsheet pleasant to look at, such as emulating a lab notebook. Unfortunately, this will make the data more difficult to easily use, reuse, and share. While data in spreadsheets has a dichotomy between human-readability and machine-readability, machine-readability should take precedence.
There are other methods to make data-entry easier, such as using a data-entry form connected to a database (i.e. SQL or Access) or spreadsheet (Excel or Google Sheets). Similarly, there are other methods to best present the data, such as visualizations or formatted tables. However, in order to use visualizations - and reuse the same visualization on similar data - the data must be organized in a manner where computer programs can easily read them.
In general, data in a spreadsheet should be organized with columns of variables, and rows of observation. Each column and row should represent one thing, either one variable or one observation. Research is easier to perform and reproduce if the data structure is determined prior to conducting research.
Common Data Formatting Errors in Spreadsheets (and how to avoid them)