How to choose an SEO company?
Reviews from past clients is a very good start. Check their website, yelp page or LinkedIn profile to see what others have to say about them. Check their rankings or case studies and see how long their process takes and how successful it has been.
Are the staff friendly and courteous when you call or email? Do they take the time to answer all of your questions or do they rush you through and try to get you off the phone as quick as possible?
If you can meet them in person you may be able to get a better feel for them as a person and judge their character. Always have an open mind when you talk to them and not every SEO company is the same.