WordPress Security?

So I have been looking around on the forums and it seems like some people have had there wp sites hacked. I am staying up to date with all wp updates, but I had a few questions since I am new to wordpress. If some one does end up hacking your site, would they be able to compromise other sites on your hosting plan. I host with bigxhosting.com and have one of the deluxe plans with them. I have not had any problems, but because it is a shared plan, or what some companies call a “reseller” plan. I just wanted to get some feed back. What can I do to take preventative measures?