Very nice guidelines but with regards to performance point 11 doesn't make sense to me.

"11. More WHERE clause hints - Avoid unnecessary conditions in the WHERE Clause. You can easily use the first example instead of the second one. The second example uses one extra OR condition which can be avoided using the first example."

The example shows first query with an OR clause like:

--Where emp_domain = 'EDU' or emp_domain = 'edu'

against

--Where Lower(emp_domain) = 'edu'

Isn't the function in most cases slower than the OR clause? At least that's what I was taught and in most cases I tested this was the case.

[Edit] Looks Like Gail already answered this.