There is no doubting that home form is going to be key. Given the strength of the Group and the fact that teams appear relatively evenly matched and certainly capable of taking points from one another then the ability to post a strong return from the three home fixtures will go a long way to deciding your fate.
If ten points is generally considered the benchmark for qualification then a return of seven points from games at The Etihad Stadium will likely be enough, which of course lends an even greater weight to tonights fixture.
Despite the blistering start City have made, displaying an expansive style of play not often seen in achieving entry to the Champions League, there must be a temptation for Roberto Mancini to exercise a degree of caution (as I expanded upon in this article for ChampionsLeague.ca). Napoli, with their own danger trio in Hamsik, Lavezzi and Cavani (all of whom I'm looking forwarding to seeing in the flesh) will pose a threat and Mancini will certainly be wary of avoiding starting the campaign with a defeat that could be damaging in the long term.
A concern tonight though for Mancini in this regard will be in midfield, with Nigel de Jong absent and both Gareth Barry and James Milner fitness doubts. Ian Ladyman tweeted that Mancini will almost certainly gamble on Barry (with fixtures against Fulham and Birmingham to come where he can be rested), whose potential partnership with Yaya Toure will be a vital one not only in shielding the Kompany/Lescott axis and stymying the threat from Napoli's front players but in providing the foundation for the attacking style we have witness so far this season.