Unless your motion is a total dud (in which case you wouldn't have brought in the first place), I would NEVER waive oral argument, especially on a motion that I took the time and expense to prepare and file. Just because the tentative is against you doesn't mean you'll lose. There are many reasons for a tentative to go against you. Perhaps the person who worked up the motion missed an important case cited, or misunderstood an important point of law and/or fact. Or one of the papers you filed never found its way to the judge. Those things happen all the time. Many times I have arrived in court for a hearing to find a tentative ruling against me, that I was able to reverse through oral argument. Judges today are overworked, with large caseloads and light staff. Go into oral argument and, at minimum, press the main points of your motion. That alone may cause the judge to see the matter differently. It may also invite discussion into the finer points of your motion that might have been missed during the court's preparation for the hearing. If nothing else, it will give you an opportunity for some face time with the judge, as well as an opportunity to 'tell your story' and remind your judge what your case is all about. That's very valuable in the big picture. No matter what the final outcome will be at the hearing, I believe you absolutely should appear and argue your motion. Let's face it, the tentative is against you so have nothing to lose and everything to gain by appearing.
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I'm not sure I agree about arguing the tentative, if all you are going to do is repeat what is in your papers and it is clear that the tentative ruling considered and rejected your argument. The analysis is different if all the tentative says is "motion denied." The court also may get angry if all you do is repeat what is in your papers (I have seen that happen). In any event, the Court of Appeal will not care if you submitted on the papers and did not challenge the tentative.