Intro GUI Text Script...

In the game I am working on, When the first level starts, I want to make a few GUI texts appear, one after the other. I don't know if I should script each text inside a script, or should I make premade gui texts and have them appear and disappear..?

It really doesn't matter. Whatever's easier for you.

But the problem is I don't actually know how to do either one...

For multiple lines, it seems easiest to make one GUIText, and then child the other lines to it. The scale is (0,1)(0,1), so (0.5,0.5) is in the center. You won't see them until Play. Maybe best to Play, tweak them where they look good, then change the settings "for real" after Stop.

This is some mostly tested demo code in C# to change the message (lineTwo is childed to the GUIText with the script. The script is on the parent GUIText):

void Start () {
  StartCoroutine(showStuff());
}

// A predone set of messages over time
IEnumerator showStuff() {
  transform.guiText.text="Firing...";
  yield return new WaitForSeconds(2);
  transform.guiText.text="Missile is fired";
  // put some text in second line:
  transform.Find("lineTwo").guiText.text="Woe to them";
  yield return new WaitForSeconds(2);
  transform.guiText.text="";
  transform.Find("lineTwo").guiText.text="";
}

// someone else can call this for any 1-time message:
public IEnumerator flashMessage(string msg, float len) {
  transform.guiText.text=msg;
  yield return new WaitForSeconds(len);
  transform.Find("lineTwo").guiText.text="l";
}