A sacrifice to the Gods is a way of bonding, of kharis. It's a way of showing our devotion to the Gods and bringing Them, actively, into our homes and lives. It's a way of acknowledging Their greatness and recognizing our loyalty to Them. Practically, this means that whatever the sacrifice, it should be given with this kharis in mind. It should be given with love, dedication and with respect to the bond between immortal and mortal.
On to the sponde: a sponde is a libation given, partly, to the Deity or Deities offered to, and partly drunken by those given the libation. Most sacrifices, especially animal sacrifices, worked with this principle, called thyesthai (θύεσθαι). They are appropriate for the Olympic Deities. There are two types of sponde: one used as a toast--usually to Hestia and/or the Agathós Daímōn--and one as a general libation.
A sponde to Hestia and/or the Agathós Daímōn is always a measure of wine. It is traditionally poured on the floor, but may also be poured onto a dish to be taken out after the meal or be poured into a potted plant or measure of earth in a pot. Some people give the sponde before the meal, others after the meal, and some give both before and after the meal, as a way of thanking Hestia and/or the Daímōn for the meal.
A general sponde is a measure of wine, oil, honey, milk or even water. It may be poured to any God or Goddess, nature spirit, Titan or hero who is not Khthonic. It may be poured on the ground, in a bowl, a potted plant or even in a fire. The latter has my personal preference because the vapors are allowed to rise to the Gods. Be careful when pouring our wine, though; the alcohol can cause a flare.
A sponde, no matter to whom, is poured in a specific manner. After the procession, cleansing, hymns and prayers, the Spondophoroi (Σπονδοφοροί), the vessel which holds the sponde, is held up in the right hand, and presented to the Gods. It is dedicated to the Deity or Deities who will receive it. Then, the Spondophoroi is transfered to the left hand and a sponde is poured to Hestia first, then, possibly to the Gods who rule this zodiacal month, and then to whomever the sponde was intended for. Then, Hestia receives the last sponde before practitioners divide the remaining content between them. The ritual can then be continued or ended.
A khoe is a type of libation which is reserved for Khthonic Theoi and other Underworld beings, like spirits or ghosts, as well as earth deities. It consists of a measure of honey, milk and dark-red wine. The major difference with the sponde is that in a khoe, the entire content is poured out; the practitioner drinks nothing of it, like with a holókaustos. The only acceptable way to pour a khoe is to pour it directly onto the ground, often in, or around, a rectangular hole which was dug by the practitioner.
A khou is poured from a khoi, a large vessel which is tipped over or slowly emptied while (most often) remaining in contact with the ground.
A libation is a an easy sacrifice which can be accomplished with hardly any material requirements. All you need is a bottle of wine and a bit of ground. A libation can be as long or intricate as the practitioner desires. Just remember that it's the thought that counts, not the physical actions.