How do you file a patent? Is it difficult?

As your profile doesn’t indicate where you live I’m going to assume you’re in the US so check here

Doesn’t look to hard as you can do it all online (I think , to be honest I didn’t look that hard).

It’s pretty easy to file a provisional patent yourself. If you’re thinking of filing a patent, you should do this first. It will backdate your patent to the date of the provisional patent, but give you a year to file your patent before you lose rights. It costs a hundred bucks or so, and it’s easy to do.

Filing a proper patent can vary wildly in cost and complexity. You can do it yourself, though depending on your background and experience it may not end up getting accepted. You can also spend 20k-50k doing it with a patent professional (more for international patents). Remember also, this process can take years, and even with a patent you’re not guaranteed it will hold up in court.

The first thing I’d recommend is deciding if a patent makes sense—often it doesn’t. Also you should do an exhaustive patent search (http://www.google.com/patents is great). If you’re still convinced it’s worth it, go to the library and read some books about patents, they should help out.

Remember: Friendster has the patent for social networks, but I’d much rather be Facebook.