Some food for thought.
Why do you want to be an O/O? Faster truck? More chicken-lights? How about a "big ol' hood sticking out in front of you like some massive phallic symbol? If those are your reasons, proceed as you wish because you're doomed to fail from the start. Most O/Os are making peanuts, have no retirement program in place and many have no healthcare (Psst, look at the teeth).
In any case, the short answer to your question is *homework*, careful prior planning, saving $$$, and self-discipline. Think everything through and really put the pencil to it. Figure worst case on all expenses and you'll be close to correct.
The much longer answer is a lot more involved than you would think. I'm an O/O leased to a generic company and it suits me for specific reasons. I drive a very simple truck and have never made truck payments. If I wanted a really nice truck I would spend much more time on the road and still do no better than a company driver with a decent company.
Think about it; Schneider can buy, finance, insure, maintain and repair a truck cheaper than you can. How can you give someone else a piece of the profit, shoulder all the expenses and do better than companies that are making pennies on the dollar? Do you think trucking companies are going to O/Os because they're swell guys? =0) Nope. It's because we absorb all the headaches and expenses.
You might want to consider two other options. You could become a trainer and make more than most O/Os. You could keep your record clean and make a concerted effort to get on with a union company.
Yes, you'll drive slow cheapie trucks, run the same boring routes and endure **** until you gain some seniority, but the pay, retirement and bennies are awesome and that's what it's all about.
Still interested or have *specific* questions? Come on back and we'll try to help. Right now you're asking for a book and I don't intend that as an insult. You deserve a pat on the back for checking things out in the first place. Many O/Os just jump into those $1,000 down deals and hit the road. =0(