Take an extension cable
Conferences are notorious for having too few and too short power leads, and everyone needs to recharge laptops, especially in hands-on sessions like tutorial day. Having an extension cable will make you instant friends as you bring power to more people.
Join in the pre-conference hype
Follow the nominated twitter tag and log into the IRC channel if there is one. Find out who is staying in the same place as you or arriving at the same time, arrange to travel together or meet for a pre-conference drink to break the ice.
Attend the extra-curricular events
Don't think for a moment that when the official schedule ends, you are off-duty for the night! Find out about any social activities going on - and if there is an informal track such as an unconference, make sure you attend, or even participate. This is a great opportunity to meet more people and see more talks in a much less structured environment.
Take business cards
Or if you don't have that kind of job (or even if you do!) get some moo cards to take with you so you can pass on your blog/email address, name and twitter details to people you want to stay in touch with after the event.
Stay an extra day
The party starts when the conference ends, so hang around for 24 hours or so and join in :) Especially for the speakers (whose rooms are paid for) and those travelling internationally, there's no need to rush off straight away. Some of the best times I've had at conferences have been after the main event.
Keep in touch
Write up your experiences on your blog (do you have a blog? If not, this is a great place to start) and tag it appropriately. Comment on other people's and stay in touch with the new friends that you made at the conference.
OK, so technically this is six ways to make friends, but I won't apologise for that :) What's your top tip for conference attendees?