What are the best practices for importing and aggregating tracks (in my case in 'plt' format) in a PostGIS table, grouped by user. Are there any tools/db models/tutorials available?
PLT format I don't know.
but to aggregate the points to lines when you have it in PostGIS is easy. use ST_MakeLine
CREATE TABLE tracklines as SELECT ST_MakeLine(the_geom) as the_geom FROM (SELECT * FROM trackpoints ORDER BY timestamp) a GROUP BY user;