How do I know when to rotate my tires and replace them?

I have a 2009 Ninja 250r. Love it. Ride it everyday and have about 6800 miles on it. Due to where i work I exit the freeways everyday turning right. The rear tire has more wear on the right side (of course) but was wondering, my tread is also getting low and im starting to get cracks in the side walls. Should i even bother rotating to balance it out? Or just replace my tires in general? Thank You. Ride Safe. (^_^)|||I rotate my tires every 10,000 miles... the correct miles are 5-6,000 miles. If you have cracks in your side walls, it's time to replace your tires. Go to a tire shop and they will tell you if the tires are worn to much and need replaced. If I find it hard to get traction when it rains or in snow I replace my tires, don't care if tire shop say they are safe. The life I save may be my own.|||When you can no longer out run the cops! LOL|||I rotate every 5000 miles and replace when the tred is worn (usually around the waranty for the tire although some drivers will wear them out sooner)|||With the cracking you should replace them for safety sake. Usually when the tire gets down to the Tread Wear Indicator in the grooves in the tread, that's when its time to replace them.|||the worst thing u can have is bad tires for a bike .the money isn't worth your life . bald tires ya ride the but not in rain. but if you have cracks in the side wall ,man there will be a comment on your gravestone that say s "por so and so ,was winning the race, but he wanted to save money buy driving 1 more week on his tires. well at least he saved his money for his passage to heaven" ya any cracks warps or bubbles any discolerd rubber or speed wabels u shoud just get knew 1s