I make mine like hannah and SS. EVOO, balsamic vinager, squirt of mustard, salt, pepper, sometimes garlic powder and basil...
(Don't use straight chopped garlic if you're not going to eat it soon after you make it--I've read using it in dressing can lead to botulism...I don't know enough about it, but used to make mine w/ fresh garlic and was totally freaked out by this...)
Best is homemade ceasar dressing:
Extra virgin olive oil
white wine vinegar
Worchesteshire or anchovy paste