generating SQL script that produces INSERT statements

In the course of narrowing down a database I would like to generate a script from within SQLPLus that selects only a few columns of certain tables and writes the result out into a file such that it can be used for importing the data later.

The database consists of 5 tables, each having a couple of columns from which I only need three or four. So wiping out the rest of the columns on each table could lead to the same effect. So copying selectively columns from the respective tables into placeholder tables could also be a solution. Only I have to rename the placeholder tables finally to the old table names after having deleted the old tables with their contents.