The most important thing to be concerned with is that the issuing bank/CD is FDIC insured. 99.99% of the CDs through the brokerages are FDIC insured. In the past 15 years, I've only seen one, secondary market on Etrade's platform that was not FDIC insured and there were big red asterisks all over the place pointing that out.
Now, as far as avoiding callable CDs - I disagree with that. If the terms provide what you're looking for, then there is no reason not to purchase it. In the secondary market, at times, you can find some real gems and the folks who go by this rule of thumb avoid them and miss out...which is fine, for those who are happy with what they provide. If there's a callable CD with a coupon so low that it would never be called, then why wouldn't you buy it? It's "effectively non-callable" at that point. Let's say there's a 5 year, callable CD, with 1% coupon and yield to maturity of 6% - you pay 75 for it ($750 per $1000 CD). The bank will never call this CD...unless interest rates fall below 1%. So, again, why wouldn't you buy it?