Dan Kennedy shares five tips on Entrepreneur.com about decreasing interruptions and increasing productivity:

1. Get lost. Don’t be so accessible. Go away, close your door, etc.
2. Don’t answer the phone. Don’t be “wide open to inbound calls.” Best approach – use a receptionist or secretary, or otherwise use voice mail.
3. Get a grip on email, texts and faxes. Train your customers, associates, employees, vendors and others to communicate with you no more frequently than some agreed upon number of times per day or week with the expectation of a delayed response.
4. Set the timer on the bomb. Set up an exit time at the start of a phone call / meeting.
5. Be busy and be obvious about it. Don’t be an easy-to-interrupt target.

A couple of comments:

1. The above tips are targeted at entrepreneurs. There are some very good tips above.

2. When collaborating with others is a vital part of getting your / their / “our” work done, especially across time zones, improving the productivity of the whole may require the allowance of more interruptions. I guess it depends on how structured the collaboration is going to be, and whether there are very clearly / tightly defined roles and contribution structures / timeframes, or if things are more fluid. You will need to discuss what is good / bad practice among the collaborators, and come to some tentative conclusions / agreements about how to proceed.