I love picnics, and use almost any excuse to stage one...
some of my favorite things to pack include:
Fried Chicken / Cold Roast Chicken
Goanese Roast Pork
depending upon the main course, favorite sides include potato salad; cole slaw; maque choux, cucumber salad; deviled eggs, assorted crudites,
"essentials" that almost always make the trip: mustard, cornichons, baguettes, cheese, fresh fruit in season.
for dessert we like: pie (I have a picnic basket that has a special compartment to hold a large Pyrex pie plate
), brownies, lemon coconut squares, coconut pound cake, other cookies.
and of course a couple of well chilled bottles of white or rose wine.