A lot of opinions on this subject!!
Some will tell you to go and rip on it for the first 30 miles and then go home and change the oil. This has worked for many and you can end up with a fast motor doing this but I bet it will burn oil and end up not lasting as long. This is not how I break in my motors!!
Really the best thing to do is very your speed and rpm's plus be sure and shift using all gears. Don't spend any length of time at one speed. This allows everything to seat evenly!!
I pretty much follow the break in recommendations by the manufacture. I figure they built it so they know what is best. I start out really easy at first and then slowly work the motor and get more aggressive as time goes on. By the time I have 900 miles on the clock I am having a pretty good time on it. At 1,000 miles its open game. However I am very gentle in the first 100 to 500 miles. When the motor is brand new you can feel how tight it is but it loosens up in the first 1,000 miles. Especially at higher rpm's.
The 4,000 rpm's under 500 miles and 6,000 rpm's under 1000 miles rule is a pretty good guide to follow. Only problem with the Ninja 500 is the engine really does not like to hang out much below 4,000 rpm's unless you are going down a hill. So for the Ninja 500 I have added about a 1,000 rpm's to each figure.
I also think its a really good idea to change the oil in the first 50 to 100 miles then again at the 600 mile service. You don't have to do it but you would be shocked what comes out of the first change. The sooner you get that gray looking oil the better. Of coarse some say keep it in as the metal flakes in the oil help everything break in better but I don't buy that.