List of the most often used introductory words:

КСТАТИ – by the way

ПО КРАЙНЕЙ МЕРЕ – at least

ВООБЩЕ – generally

ВПРОЧЕМ – however, but

ПОЭТОМУ – therefore, thus, so

В ПРИНЦИПЕ – basically, as a matter of principle

ПО СУТИ – in fact

К СЧАСТЬЮ – fortunately

К СОЖАЛЕНИЮ – unfortunately

ОПРЕДЕЛЁННО – certainly, definitely


В САМОМ ДЕЛЕ – really, indeed

ПО-МОЕМУ – as I think

НАКОНЕЦ – finally, at last

КОНЕЧНО – of course, surely

К УДИВЛЕНИЮ – surprisingly

ВО-ПЕРВЫХ – first of all

ВО-ВТОРЫХ – secondly

НАПРИМЕР – for example

In writing, introductory words are always separated by comma.