There are many reasons why people either succeed or fail in making or opposing anti-SLAPP motions. But by far the most common is the failure to properly deal with evidence. Too often I see plaintiffs spending an inordinate amount of time rebutting defendant’s contention that the alleged speech arises under the first prong of the anti-SLAPP statute. Instead, plaintiffs should be focusing on producing evidence to meet their burden under the second prong to show a "probability of prevailing" on the merits. For example, if one of the claims is for defamation, plaintiff should include evidence of damages, which may be required unless the claim is a specific type of defamation.
Typically, parties fail to lay a proper foundation for their evidence, or they attempt to introduce statements which are hearsay. When this happens, a good lawyer will file written objections to the evidence in an effort to get the court to rule that the proposed evidence is inadmissible. This is important for two reasons. First, as a defendant, if you can show that plaintiff’s evidence is inadmissible, you may prevail on the anti-SLAPP motion. Second, making written objections (or an objection orally at the hearing) is necessary to preserve those objections on appeal. If you do not make the objection either in writing before the appeal or orally at the hearing on the anti-SLAPP motion, the appellate court treats those objections as waived.
Another point to remember is that it is no longer necessary to ask the court to make a ruling on an objection during the hearing. Since some judges will not provide written rulings to objections to evidence, attorneys used to be required to make an effort to get judges to make those rulings at the hearing, e.g. "Your honor, what is your ruling on Objection No. 3." If the attorney didn’t at least make an effort on the record (even if they submitted written objections in advance) the appellate courts would treat the objections as waived for purposes of appellate review. The California Supreme Court changed that rule in 2010. Given the Supreme Court’s decision, reviewing courts treat objections in those types of situations as having been overruled. In other words, the evidence will be admitted.
On the flipside, you should only make good objections. Do not try the shotgun approach because judges do not like it. They already have enough work to do and you should endeavor to make their jobs as easy as possible. Only focus on the other side’s evidence that may make a difference to your case.