What would have motivated these attempts? How would they have been financed? Who would have been in charge when they arrived? How would they have interacted with any local populations?
I know information on early Greek settlement might be lacking, but I am interested in later attempts through the Hellenistic Age. For example, I know colonization was crucial for the Successor states, but I don't know how they went about colonizing.
Thank you!
My area of interest primarily concerns archaic Greek colonization, so I will approach some of your questions from that angle and hope that someone else will approach the question of post-Alexandrian colonization. This is actually a very important distinction to make, and not just because of the immense temporal gap, nor because of the macro-political change that Alexander brought, but because post-Alexandrian colonization represents a departure from an important theme of the Ancient Greek political ecology: the central place of the sea as a conduit of trade and communication.
Returning to the question of the earliest colonies, it is important to first consider the societies that colonists departed form, and to what extent we can consider those societies polities in the same sense as the well-known 5th century BCE city states. The answer is an unsatisfying one: "Maybe, and definitely with great variation." There remains a great deal of disagreement over when the Greek city state began to take the form it held at its developmental apogee, with scholarly opinion stretching from options as broad as (1) to emphasize the possibility that the polis (πόλις: ancient Greek word for city-state) retains, at its core, influences from Mycenaean Civilization. This is a fringe, unlikely, and ultimately unsupportable view; (2) that the Greeks came under the influence of Phoenician peoples on Cyprus and Sicily; and (3) to your question, the possibility that colonization was a major catalyst in the formation of the Greek city state.
The final option is very intriguing to me these days, and will also allow us to get to the center of some of your questions. The basic idea is that the Greeks of the "mainland" (consider this the territorial bounds of modern Greece + a few adjacent areas) had not yet crystallized into coherent, polis-style, political units in the 9th/8th century BCE. When colonists from these groups arrived to their destination, the pressure of living in an entirely foreign setting, perhaps surrounded by hostile locals, incentivized them to develop the institutions that we associate with Greek city state culture. These institutions were then exported back to the "homeland" through the considerable maritime trade networks that were beginning to spring up in that period of Greek history.
Interaction with local populations could vary from amicable to completely hostile. The sixth book of Thucydides includes a number of anecdotes about the fate of Greek colonists in Sicily during the Greek Age of Colonization: (1) Thucydides claims that the foundation of Syracuse began with the Greek colonists driving the native Sicels away from the site of their future citadel (6.3); (2) On the other hand, Thucydides notes in the next section (6.4), that Hyblaean Megara was founded when a local Sicilian power holder offered its territory to a group of Megarian colonists in dire straits.
Bibliography/Further Reading: (1) Hansen, Mogens "Polis" (2) Ober, Josiah "The Rise and Fall of Classical Greece"
As a follow-on question, we hear a lot about the the Greeks founding colonies, but they seem to be in the context of them springing up in a vacuum. Surely someone lived there first, particularly in the prime coastal locations that the Greeks favored? Were the indigenous people wiped out? Pushed aside? Accomodations made? I would think that it would be difficult for a few shiploads of Greeks, even with some technological superiority, to displace established peoples.