Most companies offer search engine optimization, paid inclusion, paid placement, contextual advertising, and specialized search marketing. Based on your needs you should be able to find a company that is right for you. If you search through the websites, you can see the Alexa rankings, read some of the website content and make decisions on the style of marketing provided on the different sites. You might find a site you really like the look and feel of and it appears they have a large number of hits based on the content. That might be the search marketing company you want to use for your site.
There are plenty of blog sites you can visit and find out for search marketing companies are the best. This will also allow you to find out which sites have provided data that is stolen or not valid for use. If you know which marketing company you want to use then you can also go to blogs and chats to find out if who you want is credible. You might like their work but they might have a bad reputation.
You should know that search engine marketing company such as a search engine optimization (SEO) is extremely important to people that are looking to make a positive income off of the internet. It allows search engines to notice your site based off of a particular number of keywords that you insert into your site. Many people put these keywords in things that they have written for their site in hopes that they will reach the number one slot on search engines.