One of the most important aspect for the outsourcing partners is to ensure that there is a continuous communication between the partners. This is true even in cases when there may not be any specific issue requiring serious discussion. The way it helps is that it keeps the channel open for any new idea or the process improvement or new development. It also helps the Principal partner who has outsourced the business function to be in the know of what is happening on the work front other side.
In my 10 years of experience with outsourcing I have seen that when this kind of communication is breached there is always a distortion that creeps in the system. Either the outsourcing partner begins to lose track of the work or the actual issues when they arise are not tackled with priority. Things are taken for granted as gradually the scope of the work gets blurred in the mind of the outsourcer and his team. Reality hits both sides when the problem arises due to change in the business environment or the assumptions on which the outsourcing arrangement was based. Say a new rate of tax has been introduced on case of an overseas client or new compliance has been introduced both sides may feel that this ought to have been communicated and handled by the other side. Sometimes simple things as regular communication keeps both sides in the loop and prevents misunderstanding.
Apart from regular interactions what is also important for an outsourcing service provider, especially for those having overseas client is to know the nuances of the local culture to be able to understand the message not explicitly spoken. So an innocuous looking question such as "do you think you need to relook at the process?" could be a complaint or unhappiness with recent deliveries. Or a question requesting to know whether you have had any change in the staff or H R policy should alert the service providers whether he needs to probe further and provoke discussions on the quality or timeliness of the deliverables. One has to understand that different cultures have different ways of communicating their unhappiness and it need not be always expressed explicitly.
It is extremely important therefore that regular communication between the two outsourcing partners is a must.