Disclaimer: in the introduction chapter.
Chapter 1: Those that you should leave alone...
This is a surprising subject in a hostage taking guide but their are some Autobots that are not worth the time and energy that goes into taking a hostage, some have been claimed by other Decepticons as their rivals and targets and other Autobots have proven that capturing them as hostages makes it easier for them to do their jobs.
Optimus Prime
He's the Prime and Lord Megatron has called what the humans called 'dibs' on ending his life, taking him as a hostage will earn you respect from many Decepticons and the interest of our Lord, it's keeping him as a hostage that's the problem.
Ratchet
Their medic, taking him as a hostage is possible but remember to watch out for the wrenches, he can be found treating Autobots in the field but to get to him, you will have to fight through groups of Autobots that won't be happy that you're attempting to break one of their codes.
Any Autobot femme stationed on Earth
Many of the mechs in the Autobots will not be happy that you are attempting to take their mate or sister or their friend or the fact that you're trying to hurt a femme, they will respond with lethal force and you don't want to know what a femme can do to you when they're mad.
This can also apply to those who are bonded.
Espionage Agents
Don't even think about it, you're just giving them a V.I.P pass to our base and you will be blamed for anything that happens if things go wrong while they're your hostage.