That is correct. There are two semi-divisions of the Gods in Greek religion, one being ouranic (heavenly) and the other being chthonic (of the underworld/dead). However, most chthonic deities and spirits have ouranic epithets or titles to sacrifice to during ritual.
Burning the offering is the traditional way to give to ouranic Gods (food or libation); burying the offering or pouring it all out without cutting it with water is proper for chthonic deities and the dead. The worshipers share the offering with ouranic deities, and chthonic ones recieve all the offering.
However, modern worship allows some freedoms. Not everyone can have a fire inside their house, and some people definitely do not have the space to burn them outside. Giving and leaving them on shrines is perfectly fine. You can dispose of them by leaving them outside/pouring them on the ground.
Typically, you start by lighting a candle for Hestia (you could also have a perpetual candle on the altar, but it's okay not to). A standard service beings by washing oneself with lustral water. Step back and contemplate why you are doing this, what the gods mean to you, etc. Walk to the altar. Then, sacred grains are thrown onto the altar (most use barely). You say a hymn to Hestia, then libate. You follow this process with other Gods, then libate lastly to Hestia. You're done!
Here's a video of making lustral water/khernips:
Here's a video of libations:
Note, this is an example of one way, but not the only way to go about it.