How do you decide which tests to automate? Which tests don’t you automate, and why? code example

Example 1: what not to automate in testing

Tests that should not be automated:

-Unstable test cases
-Tests that you will only run only once.
-The only exception to this rule is that
if you want to execute a test with a very large 
set of data, even if it’s only once,
then it makes sense to automate it.
-Unfinished functionality
-Visual test cases
-Also Tests that need to be run ASAP
which usually a new feature which is
developed requires a quick feedback
so testing it manually at first making sense.

Example 2: which test should be automated

We can't and shouldn't automate every test case
I would choose automation over manual
-If it is repetitive like data driven
test cases that are supposed to be tested against
multiple test data.
-If the test cases are high priority test cases
-If the functionality is critical functionality
-If the test cases are too long and too difficult to execute.
-I would automate smoke test cases and also
-I would automate regression test cases as much as possible
based on the priority

Also some tests are not the only candidates 
for automation. 
Tasks such as setting up or creating test data
for manual exploratory testing are also great
candidates for automation.