For me, Randori is an exercise in decisive, proactive positioning, movement, efficiency, and technique, all within the context of safety and flow. It isn't complete jiyuwaza.
There are of course many different tenets that help to understand how to approach it, some that I use are:
Be Proactive - Never wait for another person to initiate, even if this means simply choosing to pass someone by. Don't worry, they'll find you again later.
Never back up (if you can help it.)
Adhere to "Aiki-engagement" - that is, don't engage in a manner that gives the other person an advantage or control over you. Part of this means stay loose and don't stay with any one person for any length of time, trying to do something. The longer you do, the more likely they, or someone else, will get you.
Deal with them one-by-one, but in relation to all of them.
Move, move, move. Again, don't get stuck on a technique, or one person.
Control the space through positioning as much as possible. Try for the open space, with everyone in front of you. Stay on the outside as much as possible.
Do technique when it flows. When you do, be decisive.
Don't get caught up in frenetic energy. The goal is to survive. There are technical and strategic ways of dealing with every situation. That's part of the practice.
