1. Don't trust the polls - low turnout elections (around 50% or less) with large disparate electorates are notoriously hard for pollsters to predict accurately and US pollsters have consistently had a bad time. Leads of 3%-7% for the Democrats are too small to be clearly outside of the margin of error, the polls always miss 'shy' Republicans and then there is 'the Bradley effect' also in the Republicans favour.
2. Don't trust the media - consistently the Democrats get a rough ride and this becomes more important nearer the poll date. Some studies have found bias of 10 to 1 in the Republicans favour - Kerry had 10 times more negative stories and Bush 10 times more positive ones - this is no accident - the corporate media like to see the Republicans in power. As the election approaches expect all sorts of weird sideline narratives to dominate - focussing on the trivial 'scandals' over real issues is how the media will win it for McCain (even in these desperate economic times I think they will have people voting for Palin's wink rather than Obama's tax and healthcare plans).
3. Don't trust the count - Diebold promised to 'win it for Bush' and electronic counting of votes with no paper trail is a scary thought. Expect more imaginative ballot papers to confuse people into voting Republican and expect more dodgy counts - as in 2000 and 2004.
4. Don't trust the voter registration - expect hundreds of thousands of voters to be disenfranchised in Democratic wards in close states - one way or another they will be put off or prevented from voting whether it be 5 hour queues in poor wards in Ohio, intimidation, 'push polling' or being removed from voter rolls for having a 'similar name' to a felon. The winner decides these things and the Republicans keep winning because they decide these things.
Finally I hope for goodness sake that I am proved wrong and Obama makes history - even then, I'm not hopeful he would be any good - but surely better than McCain/Palin and their religious crowd pleasing rhetoric.