Voting with sessions

hi - i want to enable voting on my site, but i don’t want to require a
login. i realize people might clear their cookies and revote, that’s
fine for now. the questions are:

  1. how should i do this? Do i grab the id from the sessions table
    and link it with votes, or do i store the session hash in the votes
    table directly?

  2. How do i ensure the session doesn’t expire for a long time?

  3. how do i get the ‘session’ itself in rails? i.e. what does the code
    look like?

  4. when does the inital session begin? when the user firsts vists my
    site? or, do i configure this?