We've talked some about preservation of error. A trial court can be absolutely wrong, but the error cannot be appealed because the party unhappy about it did not communicate that to the trial judge so the error could be corrected then and there. Some error has special rules that must be observed to protect it. In Texas civil trials, one such rule is Texas Rule of Civil Procedure 278, which tells--to a certain extent--what is needful and optional in preserving error when the trial judge does not submit a question, definition or instruction to the jury.
Two kinds of jury questions exist. The first is the kind of which a party needs an answer to win the trial. For example, plaintiffs need to establish every fact that their cause of action requires. Another example: defendants have to establish every element of an affirmative defense, if they are going to win their affirmative defenses. The other kind of which the other party needs an answer. In the first example above, the defendants. In the second, the plaintiffs. To complain about the first kind of error, the party must submit in substantially correct form in writing the question needed. To complain about the second, that party need only object to the other side's proposed jury questions.
To complain of an omission of any definition or instruction, the party seeking it must submit it to the court in writing in substantially correct form.
The deadline for all these submissions and objections is before the jury charge--the collection of questions, instructions and definitions given to the jury--is submitted to the jury.