I did this on a three week vacation in Australia and New Zealand where they drive on the left :

1. Before driving out of a parking lot to turn onto a main road, spend a few seconds to think about the turns that you are going to need to do to get through the next intersection and into the correct lane on a multi-lane roadway.
2. Remember that the right turns are more dangerous than the left turns, which is the opposite to North America, and use a little more caution.
3. If you can, try to avoid driving in an area with multiple one way streets when you first start driving in the country. Sydney has several streets that terminate due to a park or major building spanning several blocks, and that, in combination with many one way streets, was a bit confusing, regarding trying to get to the local highway entrance, for a while after I first picked up the rental car to leave the city. I took a shuttle bus from the airport and only rented a car several days later for travel outside Sydney.
4. Following other drivers can be helpful at first.
5. Don't stress about it. You will get used to driving fairly quickly. I drove 3000 km on a multi-day one way trip from Sydney to Cairns via the scenic coastal towns, including the Blue Mountains, and after the first few minutes I was fine, even on 2 lane roundabouts (common in small towns instead of stop lights). In my experience, I found the local Australian drivers to be more disciplined (using turn signals, making proper lane changes, merging safely) than many drivers in most places in North America that I have been to. When I flew back to North America and rented a car during the one day stopover, I adjusted very quickly; it only seemed 'wierd' for a few minutes.

I did this on a three week vacation in Australia and New Zealand where they drive on the left :

1. Before driving out of a parking lot to turn onto a main road, spend a few seconds to think about the turns that you are going to need to do to get through the next intersection and into the correct lane on a multi-lane roadway.
2. Remember that the right turns are more dangerous than the left turns, which is the opposite to North America, and use a little more caution.
3. If you can, try to avoid driving in an area with multiple one way streets when you first start driving in the country. Sydney has several streets that terminate due to a park or major building spanning several blocks, and that, in combination with many one way streets, was a bit confusing, regarding trying to get to the local highway entrance, for a while after I first picked up the rental car to leave the city. I took a shuttle bus from the airport and only rented a car several days later for travel outside Sydney.
4. Following other drivers can be helpful at first.
5. Don't stress about it. You will get used to driving fairly quickly. I drove 3000 km on a multi-day one way trip from Sydney to Cairns via the scenic coastal towns, including the Blue Mountains, and after the first few minutes I was fine, even on 2 lane roundabouts (common in small towns instead of stop lights). In my experience, I found the local Australian drivers to be more disciplined (using turn signals, making proper lane changes, merging safely) than many drivers in most places in North America that I have been to. When I flew back to North America and rented a car during the one day stopover, I adjusted very quickly; it only seemed 'weird' for a few minutes.