Pro bono lawyers will work for free if you have a low enough income for some cases but for most people you will probably need to pay a little for your case. Pro bono lawyers as a general rule work in a very specific area of law usually more on the civil side like family law for divorces, adoptions, child support and immigration.
For criminal cases you are more times than not going to get a public defender for your legal defense. Generally a public defender is going to have a heavy case load, and the amount of time that they will have with you is limited, so if there are things that you can do to help them do there job, and maximize their time the better off you are going to be, so if they ask you to do or bring something make sure that you get it done.
There are often in bigger cites legal aid societies that can offer help as well. They usually are not well funded, but they can again help you to help yourself by showing you where the low cost and free legal resources are that you need to process your case.
Another source for free legal help is law schools. Lawyers in training need real world experience doing things like legal research, writing briefs and actual court room time. One of the ways that they can get the real world legal training they need is through pro bono work. These lawyers in training will work with law school faculty, civil or criminal defense lawyers as there supervisors. Law students are often more willing to spend more time with you as they are learning.
Many local courts have information pamphlets on things like divorce, traffic infractions, small claims and DUI and other common cases. The broachers will many times detail out the process and let you know what things that you will need in court with you and might suggest additional resources for you to consider. Some jurisdictions might have all of the forms in a folder or have the forms on a list and you pay for the forms that you need for your case then you take them home and fill them out.
Online there is more and more free legal information everyday but where do you start. A good place to start is the courthouse itself where your case will end up, because they have people going there everyday asking the same questions that you have, they have put lots of your questions online in FAQ’s and how to proceed online to free up the court workers time to dealing with the process.
Your Local library is a great resource. Librarians have people researching legal issues all of the time so they can often times point you at books that others have found to be very useful. You will find that most local libraries will have lots of legal self help books or books on specific legal areas written for the layman