Focus? What's that?
I'm constantly distracted by reading fic rather than writing my own.
In terms of ideas ... I have a notebook I write in whenever I get an idea that has merit. I'll also add extra bits whenever they come along, and when I'm finally ready to start on a story there's often a good set of notes to work from.
Unfortunatly, writing for both SV (over 3 years) and LnC (just starting) I now have far too many 'ideas' that are probably never gonna see the light of day.

Currently I'm desperate to finish the SV stories that have been lingering for over a year. Thankfully I finished my AU/historical/romance/Pirate SV story last week.