Problems with Serial Reading

#include <LiquidCrystal.h>

LiquidCrystal lcd(9, 8, 7, 6, 5, 4);

int buttState;

int buttNum = 0;

int greenPin = 11;
int redPin = 12;
int bluePin = 13;
int buttPin = 2;
int tempPin = 0;

float tempC;
int tempF;
float reading;
float voltage;

char firstLine[16]; //Potential problem area
char secondLine[16];

void setup()
{
  Serial.begin(9600);
  lcd.begin(16, 2);

  pinMode(greenPin, OUTPUT);
  pinMode(redPin, OUTPUT);
  pinMode(bluePin, OUTPUT);
  pinMode(buttPin, INPUT);
  pinMode(tempPin, INPUT);

  Serial.println("1st Line: ");  //Potential problem area
  while (Serial.available() == 0);
  firstLine[16] = Serial.read();
  Serial.println(firstLine);
  lcd.setCursor(0, 0);
  lcd.print(firstLine);

  Serial.println("2nd Line: ");  //Potential problem area
  secondLine[16] = Serial.read();
  while (Serial.available() == 0);
  Serial.println(secondLine);
  lcd.setCursor(0, 1);
  lcd.print(secondLine);
}

int readTemp()
{
  reading = analogRead(tempPin);
  voltage = reading * 5.0;
  voltage /= 1024.0;
  tempC = (voltage - 0.5) * 100 ;
  tempF = (tempC * 9.0 / 5.0) + 32.0;
  Serial.print(tempF); Serial.println(" degrees F");
  lcd.setCursor(13, 0);
  lcd.print(tempF);
  lcd.print("F");
}
void loop()
{
  buttState = digitalRead(buttPin);

  readTemp();

  if (buttState == LOW)
  {
    buttNum++;
  }

  if (buttNum > 3)
  {
    buttNum = 0;
  }

  if (buttNum == 1)
  {
    digitalWrite(greenPin, LOW);
  }
  else
  {
    digitalWrite(greenPin, HIGH);
  }

  if (buttNum == 2)
  {
    digitalWrite(redPin, LOW);
  }
  else
  {
    digitalWrite(redPin, HIGH);
  }

  if (buttNum == 3)
  {
    digitalWrite(bluePin, LOW);
  }
  else
  {
    digitalWrite(bluePin, HIGH);
  }

  Serial.println(firstLine);
  Serial.println(secondLine);

  delay(2000);
}