Pace - pacing is critical in a virtual environment and it's harder to assess how the pace is without visual cues. You will want to pause at several points and solicit feedback or take the pulse of the call. A simple question such as " What questions do you have about what we've covered so far?" or "What are your next steps going to be" can help check for understanding.
Energy levels (yours, theirs): Energy is key in a virtual setting. Without "seeing" people eye to eye our energy can flag. Listen back to a recorded call where you are facilitating. Notice the energy. What do you notice about the energy in the group? What is an appropriate level of energy to create?
Engagement - Engagement is key in the virtual world where the allure of mulit-tasking can be very strong. Take a look back at the Death By Conference call cartoon a few weeks back. Many webinar experts recommend an engagement change of pace every 3-5 minutes. This could be asking a question for people to respond to on chat, or taking a poll.
In virtual meetings you are hosting, consider regular pause points to pose a question, hear a different voice.
It often takes more time - One of the things we often fail to take into account is that it can take more time in the virtual domain to get things done. Process and instructions may be more time consuming. What changes might you need to make to your time line?
What other changes might you want to make in an upcoming virtual event you are leading? A great book I often recommend is Cindy Hugget's Virtual Training Basics, from ASTD Press. Although it is several years old now, it provides a very comprehensive overview of the foundations.