Tor is well-known for its security, but it is not so easy to use, as "most of the time, you also need to add some bridges".
Bridges (short for Bridge relays) are Tor relays (such as "117.199.213.96:443") that aren’t listed in the main directory. "Since there is no complete public list of them, even if your ISP is filtering connections to all the known Tor relays, they probably won’t be able to block all the bridges. "
To use Bridges, you can go to Vidalia’s Network settings page, and click "My ISP blocks connections to the Tor network", then add the bridges one by one at a time.
So, how to get bridges for Tor? The following are three ways for your choice:
1. Via Vidalia
Open the Tor client Vidalia, click the "Find Bridges Now" button and then there will be 3 bridges added automatically.
2. Via Web
Visit the Tor’s official bridge webpage, on which you can get three latest bridges.
3. Via Email
For Google, Yahoo and MIT email users, you can send an email with "get bridges" subject to the official email address of Tor: bridges@torproject.org, then you will get three newest bridges at once.
By the way, the more bridges you added, the more stable the Tor connection will be, but even though, you maybe still fail to get access to Tor, when your internet broadband speed is too slow or the censorship is too strong. In that case, you can check out some other anti-censorship tools.