As with any part of life or business, there are good and bad and each of those things is always backed by certain criteria as a benchmark. The benchmark when you are talking about SEO practices has to be increased custom as that is the real measure of success.
Of course, when you select your local SEO services agency you have no way of knowing if they are good or bad right? In actual fact, you should be able to check their credentials by way of their previous work and Search engine page rankings of companies they did SEO work for.
To get any new business you need to provide something new or have a new product line that people want, and the same can be said of marketing and brand identification. Your company may be well known in your immediate locality but how many people from further afield will have heard of you, probably only a handful.
Website design is a skill as is any expertise in SEO although plenty does claim to be 'expert' when they have very little knowledge in the field. An SEO expert company should be able to show you previous work for other clients and offer you information and figures to back it up.
A business website needs to be several things; it needs to be the gateway to the goods or services you provide. A website needs to provide enough information for customers to make informed decisions without trawling through irrelevant information.