In addition to the above, you MUST get the e-file authorization forms signed by the client, and you must hang on to those for 3 years (you sign them, too). I have one file folder per year kept (in a bright color, in the front of the closest file drawer), each year the rear-most gets pulled, shredded, and then put (empty) in front of the others.
Also, before you get the client copy printed, create (and then later delete if it's created) the e-file - doing that runs a whole second set of diagnostics looking specifically for nit-picky tidbits required or recommended for e-file. The federal e-file won't create without a "date signed" field filled in, but some of the states will, and you don't want to submit them by accident.