Best potato salad
Take as many small-to-medium potatoes as you have people, then double them. At least. This keeps for days and just gets better. Desirees are good - any potatoes that don't fall apart too much when you cook them. I often use sebagoes.
You don't need to peel the potatoes. Just cut them into 1cm cubes with the skin on. Put them into a pot of boiling water with salt, put the lid on, turn it down and leave for 10-12 minutes. Check to make sure they are cooked just right - undercooked are horrible; overcooked will taste fine but you'll have potato mush instead of salad. They should be still firm but not taste raw at all.
While the potatoes cook, cut up an onion really small. I like a red onion with desirees (as they are red-skinned), but a brown one will be fine. Put the chopped up onion in a bowl with about 2 tbs of vinegar. Red wine vinegar is good, so is white wine. If you don't have either you can use lemon juice, but you'll also need a little sugar as it's very tart. I don't like balsamic or malt in this; it's too overpowering. White is too sharp and I don't like cider vinegar at all.
When the potatoes are cooked, drain them well, maybe leave them to steam for a minute so they're as dry as possible, but don't let them cool off too much. Then put them in the bowl with the vinegar and onion. Mix this carefully so the vinegar is in contact with as much of the surfaces of the potato cubes as possible. Use a little more vinegar if you think it might not be enough, but don't go mad. Cover and leave for as long as you can - hours is fine. You can put the bowl in the fridge when it is cooler. Stir carefully from time to time if you like, but this isn't compulsory.
When you're ready to eat, add about 1/4 of a cup of finely chopped parsley and about 1/4 cup of really good mayonnaise. Don't use Eta Fat Free or anything that resembles it. When you taste mayonnaise you should not be able to taste any sugar at all. The only brands I buy are Best Foods or S&W. If I can't get those I make my own (any good cookbook should tell you how - it's not that difficult with a blender or food processor).
Mix carefully and serve.