Quick question about siphon breaks

I just got my parts delivered today and going to add my first fish tonight after setting up the plumbing. My question:



If I am going to have my returns too far under the water, or at heights that wont be predictable... how do I make siphon breaks in my return line? Just drill 2 holes about a half inch below the water surface? Do they need to be a certain size? Do I need more than 2? I have never had to use a siphon break before.