I know this differs in some ways from what some others here have defined as "Slav". What I go by is The Penguin Atlas of Ancient History (1988) by Colin McEvedy. His book is based on linguistic studies which, while usually respected, aren't always agreed upon. Most of the following posts were gleaned from notes taken long ago from The Slavs by Marija Gimbutas (1971), which I heartily recommend to interested readers.

Back when the danubian Indo-Europeans spread out (19'th century BC), the group that became the Slavs moved northward. The oldest Slavic finds are in an area from S.E. Poland into Moldavia (300 to 350 miles towards the Black Sea). They eventually settled into a 200 mile wide strip of land, the length of which stretched from where present-day Kharkov is in Russia to Berlin & Wroclaw on the west.

Slavs always chose land that was formerly forested and which had soil that could be turned with a plow made for light soil. They were not really aggressive, and since their homeland was located next to the more aggressive Balts, and on the crossroads of the north/south migration trail of the warlike Goths and the east/west trail for the migration of virtually every steppe tribe of even more warlike nomads, the Slavs spent most of their early existence hiding in the forests. Being a mounted people, the steppe nomads (Huns, Scyths, Sarmatians, etc) avoided forested areas. Since the grasslands were more productive than the forests (biologically speaking), it's my opinion that the Goths preferred those richer grasslands. In fact, from their beginnings till the dissolution of the Huns in about 500 AD, these people are referred to as 'Proto Slavs'. After 500, archeologists are able to show a continuity of Slavic settlement and are thence called 'Slavs'. They are classified as 'Early Slavs' from then till 700.

During the Proto Slav times, these people were favored as slaves by Germanic, Balt and Steppe tribes. The Slavic meaning of the word 'Slav' was 'glorious'. It's easy to see how slave merchants, plying their trade in more civilized Greece and Rome, led to the founding of the word 'slave'. "Hey, I've got a fine stock of Slavs for you to look at" came to mean "Hey, I've got some great slaves for you to look at". But the Slavs persisted. They started their own aggressive expansion, spreading north, south and west. They eventually occupied an area 8 times larger than their pre-expansion homeland. I've got much more on religion, family life politics, etc. to follow.