declaring variables

amateur here
I can't declare variables without initializing them with values, but it's bad practice to not declare all your variables at the start of your src, yes? Should I assign the unneeded variables null values and resassign the values when they're needed later on which may cause bugs, or comment out the variables at the head of the src and only actually declare them when needed?

Variables that are used only at certain parts, should be declared at their first use.
Variables that are used all over the place should be declared as soon as possible.

http://ai.neocities.org/var.html#tru -- tru(th) variable serving as a flag-panel tag to hold dynamically the believed reliability or truth-value of an idea. On Reddit see an alternative way of modeling truth values. For an inference validated by a human user, the truth-value may be set to a positive value arbitrarily set by the AI Mind Maintainer. Since a positive truth-value may be carried forward in recollections of the validated inference, $tru must be reset to zero at the end of a thought-generation module such as the Indicative module. AI coders may use the truth-value to establish modes of thought which disregard ideas in the knowledge base lacking a positive truth-value.