OPP is telling drivers to remember the following rules when using roundabouts:
When entering a roundabout:
Visual checks: Do visual checks of all vehicles already in the roundabout and those waiting to enter (including cyclists).
Look left: Traffic in the roundabout has the right-of-way. When preparing to enter the roundabout, pay special attention to the vehicles to your left. Adjust your speed or stop at the yield sign if necessary.
Adequate gap: Watch for a safe opportunity to enter the roundabout. Enter when there is an adequate gap in the circulating traffic flow. Don't enter directly beside another already in the roundabout, as that may be exiting at the next exit.
Travel counterclockwise: Once in the roundabout, always keep to the right of the central island and travel in a counterclockwise direction.
Keep moving: Once you are in the roundabout, do not stop except to avoid a collision; you have the right-of-way over entering traffic. Do not change lanes while in the roundabout. If in the inside lane and you miss your exit, you must continue around until you meet your exit again.
When exiting a roundabout:
Signal: Be sure to signal your exit and watch for pedestrians.
Maintain your lane: Stay to the left if you entered from the left lane or stay to the right if you entered from the right lane.
Maintain your position: Maintain your position relative to other vehicles.
Signal intent to exit: Once you have passed the exit before the one you want, use your right-turn signal.
Left lane exit: If exiting from the left lane, watch out for vehicles on the right that continue to circulate around the roundabout.
Most roundabouts in Ontario are two lane roundabout. I have yet come across a three lane or four lane roundabout
My general consensus for two lane roundabouts is treat the inside of the roundabout as you would a regular signaled intersection, in that you dont change lanes inside the intersection.
If you came up to the intersection on the right you exit straight, or turn right. You can't change your mind inside the intersection and turn left from the right lane. (Though this does not seem to stop a few motorists I have seen).
Alternative view of roundabouts (same principal), treat them like a continuous roadway. If you are in the right lane you dont suddenly turn fully left. Similarly if you are in the far left you dont suddenly turn fully right cutting everyone behind you off.
To add, if you did enter the roundabout incorrectly and ended up going in another direction then you originally desired, its generally best to continue through and course correct on the next roundabout or car park/parking lot.