For example, I'm using an Exar Exar SP3220EBCY-L RS-232 transceiver and the typical application loop back test shows that the EN pin is connected to GND and the SHDN pin is connected to VCC. Should I take this literally or am I suppose to assume that I'll need a pull-up/pull-down resistor?
It is usually fine to directly connect inputs to either GND or VCC. The datasheet of the device should be clear on that otherwise.
- when using devices like microcontrollers that have tri-state pins that can be configured both as input or output, then it is good practice to use a resistor (eg. 1k) to prevent the GPIO pin from being overloaded when accidentally being mis-configured.
- when pulling for example a RESET pin inactive without a resistor, you can never activate it without changing the circuit. If you had a pull up/down resistor in place, you could manually override it.