Most of the time I just do a Google search for whatever Torrent I am looking for rather then searching on a specific site. Most times I ended up downloading from The Pirate Bay because they have a lot.
The format varies but it should say before you download it.
Also, I should say that I have never had any issues with viruses or anything else, but I am on a Mac so I'm not sure about safety for PC's. You can also check the comments before you download it.