When to use pull up/down resistors on IC inputs
Generally, if the pin value is going to change then you need a pull up/down resistor and if it's static, you just connect directly to V+ or ground. For example, I2C rests high and the driving device pulls the line to 0 V so you need a resistor to limit the current and prevent a short circuit. For a digital pin, you may consider the pin's impedance to be very high. If you look at Figure 9 of your datasheet, you can see !EXTMEM is connected directly to V+.

In terms of the values, larger values will draw less current (simple Ohm's law) but will switch more slowly as the line's capacitances have to be charged through the resistor. Again, considering I2C, 4K7 is a sensible starting point between speed and current draw.