I have read that the work verification goes like this,
1) In order for the case analyst to be satisfied with your work experience, he first needs to believe that you have provided a legit work experience letter. That is on a company letter head detailing your salary, your job description, roles & responsibility etc. Next, he will use internet to verify whether or not your company is genuine. For example, he will look for the company's website and try to check whether or not the details mentioned matches as to what he finds on the internet. If your company has a good website and history, then most likely this should satisfy him.
2) If not, he will try to contact the company with the phone number he finds on the website and will make enquiries regarding the authenticity of the work experience letter, whether the candidate works/worked for the specific company and the person who signed the letter claims who he is etc.
3) If they are still not satisfied, then your application will be moved to the local visa office. Suppose you live in India, then it will be moved to New Delhi and further checks will happen. Since local VOs will have more knowledge and information when it comes to such situations. I have read cases where officers from VOs have approached the applicant's office to perform checks. Once satisfied, the application is then moved back to the primary VO to continue with other formalities.
Generally, first two points should satisfy most cases. The third point is a rare occurrence but still happens