Sound writing advice on advisor vs. adviser

Frequently my writing clients ask me which form of these words is correct. The good news is they may use either “advisor” or “adviser” … they’re synonyms that both mean “to counsel.” I must admit, though, that I was taught to use “adviser” by both my high school English teachers and my college journalism instructors, but apparently none of them ever attended Purdue University (or a handful of other institutions of higher learning) where “advisor” is the official spelling in job titles and “advisor” appears as the official spelling in their guidebooks. Regardless of which version you use, the best advice is to be consistent and stick to only one spelling throughout your piece.