I never had much problems with roundabouts when I first moved to England: road design is such that it naturally pushes you towards taking it in the right direction.
The one thing to be careful, as somebody mentioned earlier, is early morning or late evening (viz. when you are not yet 100% fully with it or when your concentration starts to wane) when one can all too easily turn onto the right hand lane, especially on country road. You can practice as much as you want on a parking lot. This won't help with this.

And as a pedestrian you need to be careful to look in the correct direction. In Sydney (which obviously gets a lot of visitors used to cars approaching on their left) many major intersections have painted on the road where pedestrian cross "Look Right" or "Look Left" as appropriate.

It is very easy to kust look in the direction you are expecting the traffic to approach and then step out ... and *& &*$#

I'm a left hand driver (UK) with experience of driver both RH and LH drive cars abroad.

The dangerous times are when you're not concentrating on the fact that you're on the wrong side. When you first pull out at the beginning of a journey. When you pull off a motorway having "cruised" for an hour. After turning off a road with little traffic.

To this end, do as much as you can to reinforce the unfamiliarity of it all (the worst thing is taking a UK car to France - if you get in through the "wrong" door, you're instantly reminded to do things differently).

So don't (IMHO) get an automatic (unless you have a weak left wrist!). Having to change gear with the "wrong" hand will constantly remind you that it's all a bit different!

Safe driving...

When we had to rent a car in England, my wife drove!

Automatic cars in Europe rental agencys tend to be luxury models. I've never driven a manual (and never will, it is against my code of ethics).

And presumably against the law as well! Is the the case in the US? Over here, if you pass your test on an automatic, that's all they'll let you drive!

No, they have no idea what kind of car you drove to get your license.

Considering the number of people I see every day who have no idea that a red light means stop, I not sure if you even need a license anymore.

"I ain't scared". But when mrsgregseattle and I drove in MA on our first date/trip, she kept putting both her hands on the ceiling and screaming with her head down everytime we went into a roundabout ... small town girl that she was, it was fairly unnerving for her. Me, I tried using my normal urban Chicago / former courier / driving style (don't look just drive, as the MA locals do). But she was clearly giving them signals to to my inherent weakness and we were trampled upon rightly. She still does this today when she wants to p*ss me off while I am driving, as it was that awful of an experience for me to be put in such a small place on the road.

As for the otherside of the road thingy, I agree with rb.sr and wideman's perspective about watching the left side. I wacked up pretty good the left side of a Budget rent-a-car on a guardrail on a sweeping left hand on-ramp a while back in my youth from that little perspective problem... Definitely get the insurance if it's your first time at it. (subsequent times have been much better)

This reminds me of the last time I was at the registry getting my license renewed. There was an elderly woman in front of me at the eye exam. The Woman said to her "Please read the 5th line from left to right" the elderly woman responded " X Y W M R O V" and the woman replied "No, Try again" The elderly lady responded again " Z U W N B A T" to which the woman from the registry said "No, try again"
Well, this went on 4 times and finally the elderly woman got it right, and had her license renewed. Yikes.

As someone who had to deal with a boss who wanted to "try" driving in the UK, here's my tip: make sure someone else is in the left-hand front seat to navigate for you. My boss didn't have any problems handling operating the car, but navigation is difficult if you're spending all your time watching the road. Also, be careful going out after dark until you're comfortable. We found that after-dark driving is more difficult trying to read road signs and so forth.

All you good people who are coming over here to "try the other side of the road", just post to say when when you are coming.

I'll take the train that day.

PS : We Brits have the same situation to handle when we visit the US, of course. But we have a third combination, when we drive our own, British-configured cars over to France. In that situation you are even more likely to make an error, for while the rules are reversed your car is not.

** - Just kidding about the train bit. Have a good time over here and drive safely.

Good grief, have you a death wish?

HOW TRUE!

Actually I believe you will find it no problem, if you get a manual car (usually much cheaper than automatic) you may have to think more about the shifting, but I was amazed at how quickly one adapts.

My problem was never on the road, just in large parking lots, I would find myself wandering over into the "proper" side.