Suzyq’s jar idea is a good way to start. People often use fiberglass insect screening as a cover on sprouting jars. Always rest your jar mouth-down at a 90 degree angle and don’t overfill it with seeds.
If you are sprouting larger seeds and beans, you can use a plastic container with holes or slits, drilled, cut or melted in it. You can melt plastic with a soldering iron, preferably very low temp. Be careful of fumes.
Your local health food store might have some sprouters or accessories for jars or special order them for you. The biggest natural food distributor, United Natural Foods, Inc., carries sprouting lids and jars from Sproutease. This will save you on shipping charges.
1) Keep your soaking containers and sprouter sterile. I use oxygen bleach and dish soap.
2) Soak your seeds well. Seeds that don’t germinate can rot and funkify the whole batch.
3) Rinse and Drain Well. Seeds need to be rinsed with cool water at least in the morning and evening, more often in warmer and drier climates. This keeps them cool and prevents them from drying out. Be sure to drain your seeds very well (Shake, baby, shake!) so none of them get too wet. This is especially important with small seeds. Sprouts that sit in water will die and rot. Make sure that your sprouts are dry before you put them in your fridge.
4) Give them air. Don’t put your sprouts in a cabinet or closet that doesn’t have good air circulation. Don’t overcrowd your sprouter with seeds. Remember that they will expand A LOT. In warmer and more humid climates it becomes more important to use a sprouter with good ventilation. Mason Jars tend to trap heat and moisture, although with more frequent rinsings of cool water, they can work.
5) Keep them at room temperature. 70 degrees Fahrenheit is ideal. This makes such a big difference in how fast sprouts grow that I’m surprised that there aren’t more solutions for warming sprouts. I’ll have to devise something in the fall to keep mine warm, probably something with a heating mat or heating pad and a cover that keeps just enough of the warm air inside to keep them warm but well-ventilated. Flats of microgreens or grasses would probably be easiest to keep warm.
That’s really all you need to know to start experimenting with some inexpensive seeds or beans and learn what works for you and in the climate of the room where you will be sprouting.