In your arraignment you probably received another court appearance date for the purpose of deciding whether you plan plead guilty or go to trial. It would not at all be unusual at this appearance for you to say you plan to go to trial, even though you know that you'll probably be pleading guilty. That's because you can always plead guilty right up to and anytime during the trial. Of course if you've already arranged a plea bargain (or are able to arrange it at the conference) you can wind up the case then and there. But if you don't have a plea bargain that you realistically think is possible, then you would explain that you think you could obtain a favorable verdict at trial and want a trial date.
At this point, depending on the state, court and judge, the judge may become involved and push for a plea bargain (which the prosecutor would likely go for since he or she has to live with the judge day in and day out). Or, the judge may take a hands-off approach and simply schedule a day for the trial. You may be pressured to explain just why you think you would win at trial. If you have done a careful analysis of your case and have spotted several areas where you think the prosecution has a weak case, you may be tempted to spill the beans. Unfortunately if you do end up at trial, you'll have alerted the prosecutor to your strategies and your chances for success will have been diminished. All things considered, it's usually better to play your trial strategy as close to your vest as possible.