The hearth goddess is the main goddess of the home. In ancient times, she was the actual fire on the hearth, which cooked, lit, and warmed the home. Offerings were made to her, daily, or even at each meal. At night, the fire was covered, but not extinguished, and then revived from the coals in the morning. She may have slept, but she never died.
We don't have so singular (and singular) a hearth today. Our stove, lights, and furnaces are different things. This does not mean that it is any less valid to honor a hearth goddess. There is no less reason to see her as existing at one and the same time in the various "hearths" of our homes, than there was to see her as existing at one and the same time on the hearths of different homes.
To establish a central presence for her, however, you may establish a shrine for her on a counter next to the stove. A picture of my hearth shrine is found here. It contains an icon of Brighid, which I painted myself and am very proud of, an oil lamp, a water bowl, and an offering bowl. When I pray to Brighid, I light the oil lamp, so as to have an actual flame in front of me.
I have honored Brighid as our hearth goddess for a long time, but there is nothing about this ritual that is unique to her. If you honor a different hearth goddess, there would be no problem with using her name instead. In fact, since traditionally it was the flame that was seen as the actual presence of the goddess, ther is not need to use a name at all; "Hearth Goddess," "Queen of the Hearth," or some such title would work as well.
The bowl of water is there for a purification which should be done before the ritual. Fire is pure by essence, and it is therefore right to be pure when approaching her.
One of the biggest problems with regular rituals is how to perform them regularly. Getting around to them is always a problem. This ritual gets around the problem neatly, in a way that is also meaningful. I perform it with each bottle of milk I use, preferably the first time I use it, but at least once while it is still in use. In this way part of an important food stuff is dedicated to our hearth goddess.
Purify yourself using the bowl of water and your usual purification ritual. Then light the lamp, saying:
Burn on our hearth, Brighid,
soure of all that is holy.
Raise your arms into the orans position and say:
bless this home
and all who dwell here,
and smile on all we own
Pour milk into the bowl, saying:
and give special care to guests
that our hospitality might honor you.
Put the bottle down, bow, and then let the lamp burn for a while before putting it out.