Fairly take and fairly give. Balance must be preserved, and only a complete idjit won't say thank you when help that was asked for was received.
When dealing with one's Gods and other etheric entities, what one gives back can truly be most anything. While, granted, certain Deities do have things They prefer as offerings, saying "thank you" can be done through various means.
One of my favorite ways, and certainly our children's favorite, too, is through song and dance. This in itself raises quite a bit of energy and is a joyful way to celebrate the Divine's presence in our lives and to thank Them for Their continued presence and aid. For us, dancing is simple, organic, and sometimes quite a bit silly and dizzying. But, this only brings about more joy and laughter that, considering the purpose and intent, does nothing but strengthen our offering. The songs that we sing are also simple. My family has songs that we sing for all of the Sabbats, as well as songs for our Gods that we sing in thanks and to praise Them. These songs are repetitive and fairly simple, allowing even the youngest of us to join in (okay, maybe not the very youngest as she's just learning to speak, but she's more than capable of being held and dancing about that way, contributing her joy to ours.)
Another simple offering that my children in particular love is in picking wildflowers and finding stones with which to place upon our Family Altar. During the warmer months, our altar is covered with flowers and small stones, as every day the children will bring in small handfuls of each to give to our Gods. We remove wilted flowers as needed, returning them to the Earth. The stones are all kept, and at this point we are in the process of collecting pretty containers to hold the stones so that they can all remain present on the altar.
Other nice offerings can consist of first portions of meals (with care being that the food is not salted,) as well as the smoldering of herbs and incense, and even the use of oil warmers. Some favorite offering items of certain Deities consist of honey, wine, herbs, and juicy red meat, so knowing your Gods and Their preferences is certainly advisable.
Though, often, that simple heart felt "thank you," expressed with sincerity and love is more than sufficient.
Throwing the Bones