You can also see the complete video of this recipe.
Remarks
It's important to keep the ratio of 3 times oil to vinegar.
The more mustard you add, the thicker your vinaigrette will be.
You can prepare your vinaigrette beforehand and keep it sealed in the fridge. If you add herbs, onion or shallot, I suggest that you put them in only at the last minute, otherwise vinaigrette will "burn" them if they stay in too long. The best method is to add these to your salad, then pour on vinaigrette just before serving.
About herbs, please note that they are not just a "cosmetic" addtion, they add both flavour and finesse to your dressing. I particularly like parsley and chives, but there are many others.
I'm sure that when you have tasted your own vinaigrette, you will never buy those ersatz vinaigrettes from the supermarket again.