I am leaving town for 3 months. I don't want my battery to go dead. What terminal should I dissconnect?

Negative. Black colored cable. 3 months...the battery may go dead anyhow do to internal resistance. Just a normally occuring problem. At least if you disconnect a lead then your battery will still be chargable when you get back. Draining a battery over time is bad and can actually destroy the battery. Good Idea.

Always disconnect the negative battery terminal first - that way if your wrench brushes against any ground surface your hand won't get toasted or worse.

negitive /why not just disconnect them both u will probably have to charge battery when u get back or get solar trickle charger and will keep battery topped up it plugs into cigarette lighter on sits in dash

negative

anyone as long as the loop is broken there is no flow of electrons.

Doesn't matter

either one - if there is no current, then there is no charge

but i usually disconnect both.