All seeds can be soaked before planting, but it's not necessarily beneficial to all seed sizes. Larger seeds are more appropriate for soaking, while smaller seeds aren't. Seeds should be soaked before planting because it increases the oxygen and moisture attained in soils, two things that are integral to plant growth. The benefit to presoaking seeds is it will speed up the germination process. That leads to plants growing faster.  To soak, put the seeds in a bowl of water for 24-48 hours before being planted outside or inside a container.