How to network in the film industry

This can be tricky. But, it is all about who you know.
In the US networking seems to be the way forward, here in the UK people are alot more reserved.
I would suggest attending film festivals, short film festivals, be friendly when your in Soho (the media network capitol of london), talk to people and generally be open and friendly.

There are alot of 'networking' events that happen throughout london, but these can be a waste of time as they are usually full of like minded actors, this is great, but it probably wont get you a job.
If you want to go and meet people who will potentially get you work and will want to work with you, be selective.
There is a great little cinema night in London Bridge, free or very cheap to attend and its all film makers, film makers who want to make shorts, features and are passionate about their work. A big bonus is there are very few actors who know about this night, so, you will for once be in minority.
Get business cards made, this is so important, get white business cards, they stand out more. If you are brave enough, carry your showreel with you. Hand it out, compliment directors on their work.
Attend any free screenings.
If you are into horror movies, a great festival full of filmmakers is Fright Fest in Central London, this is a great place to meet like minded people and 80% of the people who attend are film makers.
Members only clubs in london are hot spots for directors, casting directors and producers alike. Groucho Club, Soho House,Hospital Club. These attract producers like flys. But, you need to be a member to get in or go with a member, that is the tricky part.

Google search film screenings in your local area. Then do your research on the director.. is this a director you would like to work with? If so, when you attend the screening, drop them an email afterwards saying how much you loved their project and attached your cv and reel.

Be forward in your approach and show confidence. People live that!

Be yourself, be most of all , be a person...dont just talk about them giving you a job, talk to them like people, ask about them. (sounds easy, but you would be surprised at how many actors come across as desperate when just having a conversation)

Do your research and be yourself, be seen in the right places and get business cards.

Good luck