Get it as tight as you can before even considering software, and try and never ADR :) your audio will appear more "real" if people would actually shell out at the shooting stage for a decent sound recordist - the mixer is happier - talent is happier (no ADR !) and the end result will play much better - it's much much cheaper to not scrimp from the get go - it won't be better in post. If you really really have to - go through the edit marking the timecodes of each cue - and the most common method is to add 3 audio beeps before the first line or sa streamer creating wipes on screen - some talent prefer one or the other (or both) (mainly they'd rather it was recorded correctly in the first place!) Your main obstacle is to make sure you're recording in a large enough room to avoid any acoustic artifacts and being able to match the mic choice and position as it originally was (pole - which mic, personal mic? etc) and the perspective for each shot - it's tricky to get right enough for it to match in the mix.

Oh and try and not ADR ;p

3 beep http://ryanpeoples.wordpress.com/2009/08/19/creating-an-adr-three-beep/

http://www2.digidesign.com/digizine/archive/digizine_december03/protechniques/matt_rocker/

ADR overview

http://everything2.com/title/ADR

King Kong ADR walkthrough

http://filmsound.org/terminology/adr.htm