Jams are easier to do than you may think. The very best fruit to use is wild. I use wild strawberry, blueberry and raspberry. You can actually use just about any fruit, and even peppers making like a hot chutney. The biggest trick of all is making sure all your tools are clean and sterilized. I use mason jars, that have 2 piece lids. You cannot use plastic jars.
Taking the fresh fruit making sure they are clean, and often it is preferred not to wash small berries. If you know there is sand or anything else, I do rinse them in cold water. If your berries or fruit is not wild, do wash as it removes some pesticides.
I use pectin in my jam, there are various kinds available. The pectin is what jels and helps to preserve. You can get regular crystals, less sugar, and liquid. Each kind has a ratio of fruit to sugar, and sometimes lemon juice if the fruit is too sweet.
Begin to cook fruit on medium heat, with sugar, holding back 1 cup of sugar to add with your pectin. When the fruit mixture comes to a boil, add pectin sugar, and allow it to boil for 1 minute. Skim off the top to remove foam, or add a teaspoon of butter, that will defoam it.
Pour carefully in jars, preferable small ones, and lid. Within a few hours you should hear them all pop, meaning they are sealed.
Once you've had wild homemade berry jam, you'll never want another store bought.