The absolute best method is with a mallet, preferably one tuned to the size and fundamental frequencies of the bowls you have. If you have large number of varied sizes and tones having more than one mallet allows you to stay in the range of each related part of your set.
Best Singing bowls has a sophisticated set of mallets, precision manufactured in the United States. These mallets cover the full range of tones and sizes and allow play with a minimum of the harsh strike quality musicians call “attack”
In terms of laying out your group of bowls I always prefer to place them in tone sequence. This way you can choose to play multiple singing bowls low to high, high to low or a controlled (or not) in-between mix.