PLANNING SUMMER weekends with houseguests is perhaps one of the biggest challenges a host can face. There are many factors that go into making a weekend fun, interesting and stimulating. One of the most important things is the food, which requires planning menus, shopping for ingredients and cooking dishes so that meals are served on time and guests and family are sated.

I personally find such a challenge really kind of enjoyable, and over the past few years, I have compiled a file of recipes that can be prepared easily, that are certainly appealing and that make use of locally available foodstuffs and produce.

I like to make substantial breakfasts for guests because that meal invariably precedes or follows a long hike. For lunch, I keep it simple with self-serve sandwiches. This leaves room for more elaborate dinners that lead to lots of lingering. My summer home in Maine is on an island, so most of the recipes I turn to are best suited to the seaside, where shellfish is fresh and abundant.

Breakfasts are much more lavish during weekends with friends than they are when I prepare them for myself. There are pancakes, waffles, bacon and omelets, as well as concoctions created for a special occasion that are now requested time and again because they are so tasty, such as eggs Kevin: fried eggs with tomatoes and melted cheese.

I keep records of all meals served so that if I have the same houseguests twice during the season, I don't serve them the same thing more than once - unless, of course, they beg to have their favorite dish again.

For these build-your-own Crab Salad Sandwiches you mix lump crabmeat with a silky homemade mayonnaise for the perfect summer salad, and then set it out with makings for sandwiches.

CRAB SALAD SANDWICHES

3 cups jumbo lump crabmeat (about 1 pound)

1/4 cup Martha's Lemony

Mayonnaise (recipe follows) or best-quality store-bought

mayonnaise

1 teaspoon finely chopped fresh chervil, plus sprigs for garnish

Fresh lemon juice

Coarse salt and freshly ground

pepper

Sliced tomatoes

Mixed lettuces

Extra-virgin olive oil, for drizzling

Basil sprigs

Lightly toasted country bread

Stir together crab, mayonnaise and chopped chervil. Season with lemon juice, salt and pepper. Top with chervil sprigs.

Arrange tomatoes and lettuces on a platter. Season with salt and pepper, and drizzle with oil. Sprinkle with basil. Serve with crab salad and bread for assembling sandwiches. Makes 6-8 sandwiches.

Combining extra-virgin olive oil with safflower oil results in a richer and more luxurious emulsion than typical store-bought mayo.

MARTHA'S LEMONY MAYONNAISE

Pulse 1 large egg, 1 teaspoon extra-virgin olive oil and 1 teaspoon coarse salt in a food processor. Combine 1 cup safflower oil and a scant 1/2 cup extra-virgin olive oil. With machine running, add oil, 1 drop at a time until beginning to thicken, then very slowly pour in remaining oil until emulsified. Blend in 1 tablespoon fresh lemon juice. Transfer to a bowl. Refrigerate until ready to use (up to 2 days). Makes 1 1/2 cups.

This beautiful mix of fried eggs, cheese and heirloom tomatoes is one of Kevin Sharkey's favorite breakfasts. Serve it with toast.

EGGS KEVIN

2 teaspoons unsalted butter

3 large eggs

Coarse salt and freshly ground

pepper

1/2 cup mixed heirloom tomatoes, sliced

1/4 cup sliced or finely grated

extra-sharp cheddar cheese (1 ounce)

Heat broiler. Melt butter in an 8-inch nonstick ovenproof skillet over medium-high heat until foamy. Crack eggs into skillet, and cook until whites are almost set, about 1 1/2 minutes.

Remove from heat. Season eggs with salt and pepper, and top with tomatoes, then cheese. Broil until whites are set and cheese melts and is bubbling, about 1 minute. Serves 1 or 2.

Questions should be addressed to Ask Martha, care of Letters Department, Martha Stewart Living, 601 W. 26th St., 9th floor, New York, N.Y. 10001. Questions may also be sent by email to:

mslletters@marthastewart.com. Please include your name, address and daytime telephone number.