If there is one lesson I should teach you when it comes to concrete polishing, it's the simple fact that no two jobs are the same. This is the reason why there are so many craftsmen in the industry. When you work as a contractor, you will not go into a day of work with a set routine; thus you will learn to improvise. More importantly, you will know that coming into each project prepared is important.
You have to go into each job with absolute pessimism. Your client will want to have his or her concrete floor polished; that doesn't necessarily mean that the person took good care of it all this time. Expect everything from multiple cracks, to obvious repeat pourings of different types of concrete, to outright potholes. And even then, you will probably encounter something you've never seen before. Learn to improvise.
No two jobs are the same. Concrete of different types will likewise require different grit sizes of diamonds, so go into each job well-armed. There is no magic diamond that does them all, and don't let anyone tell you otherwise.
First and foremost, choose the right machine if you're just starting into concrete polishing. Just because a machine is pricey, it does not necessarily mean it will be the best one for the job. Going into a store and talking with salespeople regarding buying a polishing machine is risky business, and I would advise caution against this, as of course, salespeople will claim their products to be the best on the market. Always ask for a demonstration, and if they decline, take it as a sign that they're afraid the machine will be faulty. Better yet, go to Concrete Polishing website and ask around.
Polished concrete as an industry is still new, and as such it is filled with people trying to sell new equipment that are supposedly the best. Remember that salesmen are there to sell, but they do not necessarily know what is best. Ask an experienced contractor for help. The most ideal and reliable people to get equipment from are the ones who personally use them for their own business.