In a large glass bowl, place fruit and 1/2 cup sugar. Allow mixture to macerate for at least 2 hours or overnight in the refrigerator.
When you're ready to prepare the jam, place the fruit mixture, the lemon juice and the remainder of the sugar in a large, heavy bottom pot. If you have one, a wide, shallow pan will works best.
Heat over medium heat until sugar dissolves; then increase heat to medium-high.
While the fruit mixture comes to a boil, start your Hot Water Canning Bath. Place a large canning pot filled with water on the stove. Heat on high until water is boiling. Your jars should be pre-sterilized and ready to go. Keep them warm by submerging them in your canning pot as the water heats.
Meanwhile, bring fruit mixture to a boil. After sugar is dissolved and berries have softened, you can use a potato masher to press berries so they release some of their juices, but keep the texture chunky. Continue to boil mixture, stirring constantly to prevent burning on bottom of pan. Mixture will expand and foam up, then shrink back as it cooks and begins to set. If you are using a lot of strawberries, or making straight strawberry jam, be warned, strawberries like to expand and foam more than other berries, so keep a close eye on your jam so it doesn't bubble over.
Test the jam for gel set after about 15-20 minutes and you see your fruit mixture has visibly thickened. The bubbles will be fat and lazy, like bubbles coming up from a hot spring or molten lava and the mixture coats the back of a spoon but drips off with heavy, pregnant pauses between drops.
When the mixture is ready, remove jars from the canner and set them on a double layer of dish towels on your countertop. Carefully scoop the hot jam into hot jars leaving 1/4" of headspace. Gently wipe the rims of the jars with a damp paper towel to ensure nothing sticky is around the edges. Place two piece lids on the jars and tighten to just fingertip tight. Using a jar lifter, place the jars in the water canner and return to a boil. Once the pot is boiling again, process the jars for 10 minutes. Turn off heat, and carefully remove from canner and let rest undisturbed on your countertop for 12-24 hours. Store jars in dark, cool place for up to 1 year.
For canning safety:
Follow jar preparation and processing recommended by the USDA; see canning safety guidelines at http://www.freshpreserving.com