Looking ahead. then, later, next, after, afterward, thereafter, finally, now, consequently, to sum up
Establishing causal connections: the result, in conclusion, to conclude, because, for, since, consequently, accordingly, hence, thus, therefore
Time markers: now, then, later, soon, before, next, afterward, finally, meanwhile, thereafter, at the same time
Place markers: here, there, at this point, below, beside, next to, behind, in front, outside, inside
Comparing and establishing degree: and, similarly, in like manner, in the same way, just as, so ... that, also, more than, less than, beyond this
Qualifying conceding, or contrasting: but, nevertheless, on the other hand, however, despite this, still, on the contrary, conversely, if, as if, granted that, unless, whether, anyhow, although, even though, yet
Adding and intensifying: first, second, third; a, b, c, 1, 2, 3, to repeat, in addition, moreover, and, also, still, again, similarly, furthermore, finally, really, indeed
Introducing an illustration: thus, to illustrate, for example, for instance
Repeating a key word: This device keeps the main idea before the reader and carries the thread of meaning throughout a passage.
Using synonyms: Instead of repeating a key word so that it becomes monotonous, you may
References: http://www.uark.edu/campus-resources/qwrtcntr/resources/handouts/transitions.htm