Inputs
Switch
The Setup
pinMode(pin#, INPUT); // define which pin you are going to use for the reed switch digitalWrite(pin#, HIGH); // turn on the internal pull-up resistor for this pin
Now wire the reed switch between the pin defined and a arduino ground pin.
Reading the Input
digitalRead(pin#);
When you do your digitalRead(pin#); statements, a LOW returned value means reed switch is on and a HIGH means it's off.
Potentiometer
The Setup
pinMode(pin#, INPUT); // define which pin you are going to use for the potentiometer
A pot with it's end terminals wired to ground and +5vdc and it's wiper wired to a analog input pin requires no other pull-up resistor, internal or external. The pot itself will always present a proper electrical signal to the input pin.
analogRead(pin#); // read the analog value for this pin