The trick to being on the back is to remain in a straight line with the bike so the bike then behaves the same for the pilot and is merely slightly heavier. This is easy to do as when turning, the force on the passenger can only be directly down through the line of the bike so in reality the passenger doesn't have to do anything - and in fact mustn't do anything.
Don't try and stay upright as that would then be the rider steering one way and the passenger the other - this is what my Dad did on his one and only pillion ride with me - more a minor irritation than dangerous to be fair
My Mrs isn't noticeable on the back - presumably because she just goes with the bike so to speak and is from a biker family so was brought up with it.
To answer the "is it like riding a bike" question - yes it is, but given the weight and speed, you have to somewhat more deliberate when steering - and you need to counter-steer a bit more as well as shifting your weigh - although it still pretty instinctive. Any cyclist can basically get on a motorcycle and ride round quite happily - need to learn to ride it safely and / or pass a test, but basic riding along is the same.
Whether the get on the back with someone - worth asking yourself "is rider a nutter?" and even if not a nutter, will they show off or try and impress you.
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