As a Wiccan, I perform devotions and meditations on a daily basis to keep me spiritually centered, maintain dialogue with Spirit, and give thanks for my many blessings. Whenever I perform a spell or working (especially one in which I have called upon a specific deity or deities) I will often make an offering or sacrifice to that deity when my work has been successful.
Sometimes my offering may be something as simple as burning incense or a candle. I typically, light the candle and/or incense before a statue or image of the deity. I may say something as simple as
I often make offerings to my ancestors to keep them appeased and for thanking them for assisting in the many way that they do so. These offerings are usually very specific based on what my ancestors enjoyed in life. For example, my grandfather loved Luzianna Coffee so I will often offer him coffee; in addition he liked reading Louis Lamour western novels and I keep one on my ancestral altar for him.
At other times I may sacrifice something more personal such as a favored piece of jewelry, or even my hair. For example, the turtle is my totem. Once many years ago I was hiking at 40 Acre Rock when I found a whole, intact, turtle shell at the mouth of a bear cave. I took the shell for my altar, but had nothing to offer in return. At that time, my hair was about 6 inches past my shoulders, so I used a friend's knife to cut about an inch from my hair and left it as an offering in place of the shell.
Still at other times, my sacrifice will take the form of a charitable offering in the name of that deity. Recently I had been performing work in order to get my car repaired and at a price that I can afford. When my car was successfully prepared, I thanked God by filling a box with non-perishable food-stuffs and donating it to my local food bank.
Whenever I bake homemade biscuits, I always make one or two special ones which are set aside and used as an offering to the Fay Folk and this is set outside my back door with a small saucer of milk.
I think that as spiritual practitioners it is important to give thanks for our blessings, especially when we routinely petition spiritual powers to help us achieve our goals. These are just a few examples of how one can show gratitude for their many blessings.