Make sure you vary the throttle settings by speeding up and slowing down most of the time. The worst thing you can do is baby the engine and run it too slow. That will not allow the rings to seat properly.
The only thing you may want to avoid is prolonged high speed running.
It isn't going to break in sitting in the garage unused. I've gone 25 miles on first start of my engine and the hills around here ensure are perfect in ensuring that the engine load is varied on my engine and engine is worked throughout the rpm range without spending too much time at a particular engine speed.
I'd go farther but too much stuff loosens up on the first ride
In addition, to the aforementioned tools. I always throw a master link on my chain during the first couple of miles. I don't know why but its a ritual for me. You should always carry a spare master link assembly. I don't know about you, but I hate pedaling back home
Hey, whatever you do, do not lift it upon your work bench and walk away. I haven't even broke in my engine but I did manage to break 3 cooling fins, 1 sparkplug cap and bend the threaded end of the spark plug.
Needless to say, I spent a few hours fabricating a firm stand.
Definately the wrong way to break your engine in!