From the Atkinson-Baker Discovery Update: "When and How to Object During a Deposition," by Paul Mark Sandler and John J. Lovejoy--
At a deposition, an attorney is required to object to those defects that are immediately curable--that is, irregularities that opposing counsel can correct at the deposition. Such defects include procedural matters, such as the manner of taking a deposition, the form of questions or answers, the oath or affirmation, and the conduct of the parties.
Timely objections are necessary, for instance, where a question is leading, vague or unintelligible, mischaracterizes prior testimony, calls for speculation, or constitutes a compound question. Problems can also arise with answers. If the attorney taking the deposition believes the witness has not provided a responsive answer, that attorney should object accordingly.
There's much more in the complete article. The authors are lawyers at Shapiro Sher Guinot & Sandler.