There are three basic ways a criminal defense attorney can make a difference in your case.
I call these options negotiation, motion litigation, and trial. I'll explain each of these methods.
Plea agreements, also called "plea bargains" are a good option for those who are not likely to win their case at trial. If you have made a mistake and are simply looking to minimize the damage it will cause in your life, this may be your best option. There are a number of different strategies an attorney may use to negotiate an excellent plea agreement for you. To see some examples of recent plea agreements I have negotiated, look here.
There are numerous pre-trial motions your attorney can file that, if granted, can make an enormous difference in the outcome of your case. For example, if you were illegally arrested or searched, your attorney can file a motion to suppress evidence pursuant to Penal Code section 1538.5 and the 4th Amendment. When evidence is suppressed, it means the Court has ruled it inadmissible in the case against you. After a motion to suppress is granted, the prosecution will have to either dismiss the case or, at least, a portion of the case.
Other common motions pretrial motions include motions to dismiss on speedy trial grounds (Serna, PC 1382), motion to set aside an information (PC 995), motions to obtain records of officer misconduct (Pitchess), motions for a lineup (Evans), and motions to quash and traverse a search warrant.
Motion practice requires an attorney with an extensive knowledge of the law. Your attorney will also need top-notch legal research skills, writing skills, and oral argument skills. To see some examples of recent motion victories I have had, look here.
When the prosecution is unwilling to offer a plea agreement that is acceptable, or when you are simply not guilty, then you need to take your case to jury trial. With this option in particular, it is critical that you have an experienced attorney at your side. Trials require a thorough knowledge of the law, the ability to quickly think on your feet, and the experience and wisdom to present your case in the most persuasive way to a jury. I have extensive jury trial experience with both misdemeanors and felonies. To see some examples of recent victories I have had in trial, look here.