Field name in the Where - Yup
Change 1-letter in the source name: i.e. CustomerQ vs CustomerT - Yup
But honestly, the one that gets me the most is if I'm working on multiple DB's at the same time, and especially if  one or more are databases I didn't build originally, trying to use the field name from a table in one DB to represent the same field name in another, i.e. - FirstName vs NameFirst

The one that gets me all the time now is that I made a rule for myself to always make my table and query names singular. I started doing this about 10 years ago, like CustomerT instead of CustomersT. I've got some databases that I built before that, including on the website, it's CommentsT. Every time I write SQL, I forget that and it bites me. Of course I'm not going to go through the entire website and change every instance of that. It's not as easy as copy and paste and doing a find and replace in Access.

I had a bug in my own database fairly recently.

I recently built a user management system, and I was trying to enforce rules against reusing passwords, and for some reason, my code still allowed me to reuse my previous passwords even though the code I thought would work didn’t work like I expected it to.

I fixed my code by changing the where condition in my SQL statement.

“SELECT * FROM PasswordHistoryT WHERE UserID=“ & TempVars(“UserID”) & “ AND Password=‘“ & Password1 & “ OR Password=‘“ & Password2

In a nutshell, my user management system uses an ADO Recordset from SQL Server to look up previous passwords from the user who logs on. If the password they try to enter into the form exists in my Password History table, it throws up a message box saying “Can’t use a previous password.”

You are missing some quotes.

"SELECT * FROM PasswordHistoryT WHERE UserID=" & TempVars("UserID") & " AND Password='" & Password1 & "' OR Password='" & Password2 & "'"

That was my bad, I forgot to include the extra quotes in my post. Thanks Kevin!