Since it seems to be hard to avoid nomination (I mean, even Kate got nominated), I think Priority One is that the public like you. Playing it sneaky, i.e. "working" the other HMs so that they don't vote for you, is pointless, because like it or not you will be up for eviction at some point, and then the public will promptly kick you out (Adele). And anyway, you'll never win the final vote.
So you have two options:
1. Make the public like you more than the other HMs.
If you have an especially appealing and/or interesting personality, there's no problem, just relax and be yourself (Kate, Alex, Brian from BB2). But what if you're stuck with a more run-of-the-mill personality, e.g. Jonny or PJ this year? Neither of them can compete with Kate in the nice+funny+looks stakes, or Alex in the quirky+interesting+looks stakes. Which leads me to...
2. Make the public dislike the other HMs more than you.
If you can't beat them on charisma, beat them by being less hateful. The public like "salt of the earth" types, it worked for Craig in BB1. So, do everything you can, as subtly as you can, to emphasise their bad points to the viewers, and keep doing it. Right now, PJ and Jonny should encourage Alex to whinge as much as possible (shouldn't be too difficult). Kate is a bit more tricky - she's infuriatingly sane and reasonable, but their must be some chink in her armour. They should find it and exploit it, whilst appearing not to.
Whichever path you take, it is in your interest to keep the publicly-unpopular HMs around. They all suspect that Jade is unpopular, so now that it's getting down to the crunch, they should keep her there for the duration. If PJ and Jonny have any sense they'll try to hang on to Tim, too, but it seems the HMs don't realise how much the public dislike him, so he'll probably be the next to go.