Linton Hopkins's secret for making his sweet strawberry preserves is simple: Use ripe berries, and cook them at the proper temperature so you don't have to add any fruit pectin as a thickener. More Strawberry Recipes
In a large, deep skillet, pour the lemon juice around the sugar. Cook over moderate heat undisturbed until most of the sugar is melted, about 10 minutes. Gently stir the sugar until completely melted. Using a moistened pastry brush, wash down any sugar crystals from the side of the skillet.
Add the strawberries and boil over moderately high heat, mashing them gently until the preserves reach 220° (or 8° above boiling point, depending on altitude), about 10 minutes. Continue to boil until the preserves are thick, 4 minutes longer.
Spoon the preserves into 3 hot 1-pint canning jars, leaving a 1/4 inch of space at the top, and close with the lids and rings.
To process, boil the jars for 15 minutes. Let cool to room temperature and serve after 2 days or store the preserves in a cool, dark place for up to 1 year. Refrigerate after opening.
Check out Canning 101 for information on basic canning equipment and techniques.