There are many effective ways to build credit. In order to keep creditors from bothering you, and in order for you to get a loan with a reasonable interest rate, you need to learn how to build your credit. The best place to start is to not buy things that you dont need. If you always make impulse buys, you will find yourself in deeper debt very quickly. And if you have no credit history at all, you must keep that in mind.
Building good credit if you have bad credit
If you have bad credit, consult one of the many books available written by qualified financial advisors in order to get started on the right path. You can find books like these at your local library. In these books you will find checklists and step-by-step advice that will help you turn your credit around. There are also guides available at the library that can instruct those in debt on how to write letters to their creditors. Letters are probably a more effective avenue to take rather than communicating by phone, since most creditors will not be sympathetic to your situation.
Another value of the written communication is that if you should end up in court, the written documentation will be...