How to protect ADC inputs from transients and at start-up?

I'm aiming to use a Beaglebone Black to measure some voltages. I have
no problems with sorting out voltage dividers etc. to get the measured
values down to less than 1.8 volts but I'm not so sure about how to
protect the inputs against transients and at any time the Beaglebone
isn't turned on.

Firstly, what's the usual method for preventing transients getting
into the Beaglebone inputs? This will be a moderately noisy
environment (a boat with 12 volt car style electrics).

Secondly how do you ensure all the inputs are off until the Beaglebone
has come to life? The measured voltages are going to be there 'all
the time' regardless of what the Beaglebone is doing so there has to
be some way of preventing the input being actually presented to the
Beaglebone until it has powered up. Is there a standard (and simple!)
way of doing this?

There are a variety of chips designed to facilitate hot-plug or live
insertion that would probably work. See for instance the various CBT
products from TI and others, which are low-resistance pass transistors
when on, and open circuits when off. They can be used to prevent damage
when the power is off, provide voltage level translation, and in a
variety of other ways. As an example, something like the following
ought to work:

Alternately, you could put an op-amp filter/driver circuit in front of
the ADC inputs, powered by the ADC 1.8V rail. Then you have to protect
the ADC inputs, but typically there's a series resistor as part of a
filter circuit so you don't have to worry about exceeding the devices
maximum clamp current.

There are many other ways to do this as well. One of the fun things
about engineering is there are so many different ways to solve the same