Be it a large well known conference or a smaller Writers Retreat e.g. the Roman Writers Retreat www.budurl.com/RomanRetreat it's best to plan in advance and work out your goals.
Author, Cheryl Malandrinos advises "Be prepared. Review all conference materials ahead of time so that you know what to bring, directions on how to get there, and if homework or exercises will be part of any panel you are attending".
http://www.ehow.com/how_2317430_get-out-writers-conference.html offers some advice for attending writers conferences that is worth a read.
http://www.writersdigest.com/article/Getting_the_Most_Out_of_a_Writers_Conference/ has an excellent article that deals with both the before, during and after, that is a must read for anyone considering attending a writers conference.
Patricia Stoltey offers a list of ten ways to get the most out from a writers conference in her post at http://bloodredpencil.blogspot.com/2010/09/ten-ways-to-get-most-from-writers.html
The Frugal Book Promoter (www.budurl.com/FrugalBkPromo) by Carolyn Howard-Johnson is one of the few (if not, the only) books on promotion that has a section in it on making the most of a writers' conference. For promotion. For networking. For learning. It even includes a little notebook system for using a conference effectively.
Writers Conferences don't just take place as in person events anymore. The internet now offers online versions that can be equally good. In some cases they are also free to attend.
As with in person events you will want to check the schedule carefully before the event and mark the talks, workshops and people you are interested in.
It's also a good idea to check time conversions as with online events times listed might be on a different time zone.
Lea Schizas, organiser of the annual Muse Online Writers Conference (http://www.themuseonlinewritersconference.com) offers this great tip: “Mingle and don't be shy to ask questions. During a conference you have the opportunity to meet presenters who can answer your queries immediately so grab that chance and use it to the max”.