There is no easy answer to this question. There tended to be a wide variation in styles and approaches to writing. For example, if you look at just the examples in "Studies in fifth century Attic epigraphy" by Donald Bradeen, you will see a range of styles and that is just one place and time. As a rule writing was most often continuous.
I see that in the Wikipedia there is a statement that a universal standard of word separation before continuous script was used. That is not true, or at least it is an oversimplification. The use of interpuncts in the earliest greek writing is sometimes found. Continuous script was always the most common method not only in ancient Greek, but in other languages as well. It is true that some early inscriptions do use various types of word dividers, but you can find continuous letterings contemporaneously with those examples. Just as a single example of this, the oldest Greek inscription known, the Dipylon inscription, is written in a continuous lettering.
The exception to this general practice is in consonantal languages, such as semitic languages (see "Word Division in West Semitic Writing" by J. Naveh, Israel Exploration Journal, Vol. 23, No. 4 (1973), pp. 206-208). In alphabetic systems with no vowels word divisions are more important because a lot of ambiguity results if the words are not separated.
The routine use of spaces to divide word is first found in western spelling (with vowels) in early Christian Irish manuscripts of the 7th and 8th centuries. During the viking period this practice gradually spread to the rest of Europe.