"I find myself wondering what I can do as an individual to help try to defeat Trump."Easy one. Encourage registration and voting. Drive elderlies to polls.
Even in a "safely" blue state like NY/NJ, it's critical that he lose by wide margin 1. to send a message to world that USA hasn't gone crazy, and 2. to remove Trump's ability to say he lost via fraud and cheating.
Lots of of people don't vote because they assume their state is "safe". So consider on a quiet, one-to-one basis (social media is just noise), I'd suggest working to convince apathetic friends, neighbors, and relatives to 1. register and then 2. Vote. Remind them of how British non-voters felt the day after Brexit, after assuming the electorate would do the sane thing, so their vote wouldn't be needed.
I wouldn't even mention Trump. If you persuade a few dozen people to vote and a couple happen to be quiet Trump supporters, fine. Aim single-mindedly to get people registered and into voting booths, period, and leave it there. If you make your message explicitly pro-Clinton or anti-Trump, your voice will be lost amid the political noise (i.e. stating the obvious). In other words, you'll lose the one-pointedness of your message that this time, we all really need to vote.
As a centrist, I like mixed governance, and a certain amount of gridlock, and I wouldn't want Clinton to completely stack the Supreme Court (I'd prefer to see it more or less balanced). But the Republicans are so crazy this cycle, and have been so emptily obstructionist for so long, that I'd like to see Democratic majority in the Senate, as well as a Democratic president, at least for one term.
I may, therefore, donate to DNC (or to individual Democratic campaigns, e.g. the candidate trying to bring down the loathsome Darryl Issa), but not to the Clinton campaign - solely because I don't think more pro-Hillary ads will help. The smartest thing Clinton can do is let Trump be Trump . There's been no indication - in two previous national campaigns where she's squandered wide leads against seemingly unelectable opponents - that a strategy of increasing the visibility of this extraordinarily recognizable figure is the least bit useful.