Good article.  Great to know about colors!
I always start a new instance of SSMS for each database this way all tabs point to the same dm.
I resize the window that I am not working on making it tall and skinny or or short and wide so it is clear that this is the "other" DB.
When I write an ad hoc insert or delete I write it like this:
Select *
--DELETE
From TableName WHERE
A=1 AND ...
If I execute the whole page then this is just a select.  I can test the where clause with the select like the other poster said.  The WHERE hanging at the end of the line will break the query if I don't also include the conditions (that often will not fit on the same line).
I drink lot's of coffee.