One of Obama's greatest strengths is that he is simply more likable that Hillary is.  And let's not underestimate the extent to which presidential elections are popularity contests.  If experience was all that mattered, Al Gore would have won the 2000 election in a landslide.
And what is it that people don't like about Hillary?  She's a liar (a trait she shares with Bill).  She's thin skinned.  She's vindictive as hell.  She's paranoid (remember the right wing conspiracy remark?).  She's secretive to a fault, always acting like she's got something to hide.  And she plays dirty (Florida and Michigan, turning pledged delegates, etc).
Let's see: dishonest, think skinned, vindictive, paranoid, secretive, plays dirty.  Hmmm . . . reminder you of anyone else?  Ok, remind you of anyone besides Dick Cheney?  Yep, Hillary Clinton is Richard Nixon in a pantsuit.  
Whenever the Clinton campaign attacks you (which is pretty much all the time to day), in addition to challenging the merits (always to this), you need to need to turn the argument back on them by showing how their behavior exemplifies one of Hillary's many character flaws.

If Hillary's camp goes ballistic over some crude remark by an Obama staffer or the press, you need to make the case that a president is going to face such attacks all the time, and question whether Hillary is temperamentally suited for the job.  And if this provokes even more outrage from Hillary's camp so much the better -- it only proves your point.
If Hillary's camp overstates its case (e.g., a lifetime of experiences versus one speech, a request for tax returns being a Ken Starr fishing expedition), you need to pound away at how Hilary likes to play fast and loose with the truth.  And goad the press into investigating her statements rather than printing them verbatim.
Finally, keep hammering away at her unwillingness to disclose her tax returns immediately, the Clinton's refusal to reveal the identities of the library contributors, and their footdragging on the release of Clinton administration records.  The Clintons have always been a little tone deaf on the issue of transparency (going back to the secret meetings of the the health care task force) -- they instinctively act as though they have something to hide.  So this will be a gift that keeps on giving.