The exact requirements you need to fulfill to win a civil case depend upon which side of the coin you're on: plaintiff or defendant. No matter which, your chances of coming out of the trial on the right side of the verdict will be greatly enhanced if you retain the services of a qualified, experienced attorney.
Win a Civil Case as the Plaintiff
Be prepared to prove beyond a shadow of a doubt that the defendant is responsible for the items for which you're suing. If you're suing for breach of contract, be sure to produce not only the contract, but also evidence of the defendant's failure to honor it. If you're suing for damages related to injury, be prepared to present the court with witnesses who can testify that the defendant did, in fact, cause the injury.
Call the most reputable witnesses you possibly can. For example, if you were injured in a traffic accident, summon the police officer who responded to the scene to verify that the accident was, in fact, the defendant's fault.
Consider hiring expert witnesses to provide additional testimony, if needed. These are usually used if you're making a key argument that relies on conjecture or theory of some sort. Expert witnesses are used to give added weight to such arguments.
Emerge a Victorious Defendant
Review all of the charges against you with the help of your attorney. Make sure you fully understand them.
Strategize. If you can cast any shadow of doubt upon the principal claims being made in the lawsuit, thrust yourself into it. Especially in cases of contract law, the burden of proof falls on the plaintiff to prove that you did do something (as opposed to you having to prove you didn't do something).
Work to reduce the total damages of the lawsuit by showing the falsity of as many of the plaintiff's claims as possible. This way, even if you don't win the case, the judge may award sharply reduced damages than were originally asked for in the lawsuit papers.