This seems like it's mostly UPG based, so...
There is really no right or wrong way to honor Loki. There are no guidelines, no protocols, no rules. You honor Loki in your own personal way as you see fit. As long as you like it, chances are he will like it as well. There's no way to correctly give him offerings, praying to him or working with him.
Some offerings can consist of sweets (as was already mentioned) and spicy stuff. Especially Fireball. But really, any offering will do as long as it's made with love.
Speak the truth. Regardless of the Lie-Smith title, he is a god that bring the truth to the surface. Speak up when everyone is silent. He is also a god of beneficial change. Change is something everyone tries to shy away from, but Loki knows it needs to be done, and for the better.
Actually,The god of fire idea is a famous mistake that is due to the similarity between the names Loki and Logi, the latter being a personification of fire in the well-known story of Thors visit to the giant tgara-Loki. The connection to fire was popularized by the composer Richard Wagner in his Ring operas, in which he portrayed Loki as a sort of fire-sprite named Loge.
Here's some sources as well to help out newbie Lokeans.