TLDR: generating real traffic for your book and not worrying about nominations is the way to go.
Hot and trending is based on an algorithm that is completely internal to amazon. We can, however, extrapolate how it works based on similar algorithms (for example, we know that reviews with more "like if helpful" clicks are worth more than comparable reviews that aren't liked)
Most likely it takes page views and nominations into account, as well as data over several days and sticky hot and trending hours (it's harder to knock a book off of hot and trending to get on than it is to stay on once you're up there). Most likely it takes page view to nomination ratios into account as well (if 50 people look at your book in a day and only 2 nominated, then it probably is a lot worse off than 15 people looking at your book and the same 2 nominating).
It also probably takes into account how many clicks come internal links from kindle scout compared to external (did you send a friend to the site by direct link, or did someone browse KS website and decide take a look) because that would give them analytics about how good your cover is. Most likely, a browse while not on hot and trending is worth more than a browse while it is trending, because if someone will just find your book from a list of 300 books and choose to click yours, that is worth more than someone skimming a list of 20 and picking yours.
Everything probably has some averaging weight to find an overall value, and it seems that the hot and trending list is a placeholder list that is randomized over pages (ie, your book might end up in slot 5 on the hot and trending list, and over the course of the day slot 5 spends equal time on pages 1-5 of hot and trending. If you jump onto the list and take slot 5 from another author, then the slot itself continues its trek through the page listings so that no single H&T book stays on page 1 the entire time). The list is definitely random, thereby obfuscating the process even further. Also, I would bet that TSOP "Time spent on page" matters quite a bit too. If people just click the link and nominate, then scout assumes that's a friend/fan nomination, whereas if someone spends 10 minutes or so on your page reading everything you wrote, and then they nominate, scout can say "this user read and liked the entry and voted" instead of "this user is just clicking to support the author".
Essentially, it's probably a fairly complicated algorithm, but all you need to know is getting eyeballs to your page is the important thing. They added in protections because in the first year of kindle scout people could just remove and reapply their own nomination over and over again to get on and stay on hot and trending (which is why there was a flurry of "ZOMG MY BOOK WAS HOT AND TRENDING THE ENTIRE TIME AND DIDN'T GET PICKED" blog and forum posts from people complaining (hence why a lot of blog posts are utterly useless about the early days of kindle scout). Now, my bet is that someone removing and reapplying a nomination multiple times is a negative for your book (to discourage cheating) or at least has a net neutral effect on your ranking.
In any case, the only thing you can control is traffic. Getting as many people to look at your page and read the content you've provided is what gets you noticed. Analytics are insanely powerful, so their algorithm could literally include almost anything, but the paltry details they give us access to make it impossible to accurately predict which analytics they care about.