Slack is fast becoming the chosen way to communicate across businesses big and small worldwide. (If you've not heard of slack before, check out their site here.)
Many Time etc clients use Slack within their business and what better way for you as a freelance virtual assistant to become integrated with your client's way of working and build a great working relationship by being on Slack too!
There are many online guides about using Slack but the best place to start is Slacks own guide which you can view here.