4- Grammar: If the comments from that particular SEO have horrible grammar and if it apparent that text has been directly translated from some other language, you could avoid them. A comment for a comment’s sake in bad grammar is highly ineffective. True, you probably will get the link you are looking for, but what kind of an impression are you giving the site where the comment is being left?
3- Plan of Action: If the company you are talking with is talking about everything that they want to do but don’t really have a concrete plan about how to go about it, avoid them like the plague. Why? Because they will end up planning so much that they won’t leave any time to actually execute any of them. Look at what their plan of action is if it matches what they are saying.
2- Focus on PPC only: When the company is focussing only on PPC, rather than SEO as a whole, and not working towards Organic Results, it had best be avoided. The most important thing with SEO is for the search results to be organic ones, if the SEO Company is not talking to you about it, and focussing on getting you to the top pages using only paid links and ads to do so, the quality of the ranking deteriorates.
1-Keywords: If the SEO is still stuck on Keyword stuffing and Meta keywords, you can take him out of running without even thinking twice about it. Keyword stuffing is a thing of the past. Pages that have been stuffed with keywords show up on search results but are not read by anyone for the obvious reason that they make no sense. What then is the point of it?
Anything you want to add to this?