Connect before the conference:
Your networking efforts should start as soon as you decide to go to a conference or even before that. Go through the speaker list and search Twitter exhaustively to find and follow these folks, either directly or via a list. Interact with these speakers on Twitter to ask them meaningful questions. Also ask them if you can have 5 minutes of their time at the conference. Look up on LinkedIn and Plancast to identify who is going to be at the conference. Ask the organizer to send you a list of attendees. Some organizers would happily oblige. If any of these folks sound interesting, follow them on Twitter and reach out to them with a request to see them at the conference. Be specific about why you would want to see them. Do your homework to get up to the speed on some of the topics that you're interested in hearing more about at the conference. Use the conference sessions to enrich yourself and not to educate.
Be smart with your time:
Design your agenda upfront and put the sessions that you want to go to on your calendar. Spend your time wisely by not going to too many sessions. On an extreme, for certain conferences, I would suggest not to go to any sessions, at all. Differentiate between content and inspirational sessions - ask yourself why you are there. Once you sit down, you're in a zombie mode receiving content. Some speakers and panelists are good and some are not. Don't hesitate to leave or join a session in the middle. I closely monitor my Twitter stream in real-time based on a conference hashtag. If I see tweets from people praising other sessions, I walk out and go there. For asking questions, the worst time to approach a speaker is right before and right after the session. You're competing for his/her attention. Find (don't stalk) the person later on during a conference and follow up with your questions. I have sent emails to the speakers after the sessions and have received great responses.
Don't waste your time watching pitches of a vendor in the exhibit area or talking to a marketing guy/gal for the purposes of gathering information. You should research the products of vendors ahead of time and have a list of exhibits that you want to visit. Write down what you want to know and who you want to meet. Go to the booth and ask them those specific questions or demand to see a specific person. Even better, set up appointments ahead of time. If they can't answer your question or if you don't get to see the person you wanted to see, leave your business card and ask them to reach out to you. Don't become a victim of meaningless marketing and a sales pitch. Your time at a conference is far more valuable than that.
Don't miss coffee breaks and cocktail receptions:
Meet any and all people you can. Have meaningful conversations. Offer them to help and ask for help. The experts don't become experts merely based on what they think; they extensively collect information from other people and synthesize that to form a point of view. Ask yourself how you might be able to help them so that they can help you. Use your smartphone to send them a LinkedIn invitation while you are at the conference and take some notes of the conversation that you had. I typically use the back of the business card (that I receive) to take notes. Use Highlight to instrument and take advantage of serendipity.
Do not run out of business cards:
I have come across people during a conference telling me they don't have their business cards. If they are not lying, it's just ridiculous. You should never run out of business cards at a conference, ever. Keep them in your bag and keep them in your coat pocket. I even have a designated coat pocket to keep my business cards so that I don't have to shuffle things to look for one. I also use another designated pocket to collect business cards that I receive. I also keep a pen in my coat to take notes on the business cards. I keep two sets of business cards, on that has my cell phone on it and the other that has my land line on it. I never use my landline to take any incoming calls, only voicemail. If you want the person to call you, give them the ones with the mobile number on it. If not, give them the other card. Instead of a landline number you can also use a Google Voice number. Print a small QR code on your business card that directs people to your website which could be your LinkedIn page, about.me page, or your blog. Make it easy for people to find you and know more about you. Needless to say, you should have a fairly detailed profile on the internet before you decide to go to a conference. If your company doesn't allow you to print your personal social media details on your company business cards, keep two sets of cards - the business as well as the personal.
Follow-up after the conference:
This is the biggest mistake that I always see people make. Once you're back from a conference, you have only accomplished 50% of your task. Follow up with all the people whom you met. Send them emails with enough relevant information to jog their memory. The influential people meet a lot of people during a conference. So, don't just say hi, but go back to you notes and refer to a very specific conversation you had with them. Ask them if it would be okay to follow up with them. Typically no one says no, but you should ask. This gives you a right to send them a second email. Do NOT call them even if you have their phone number. That's what sales people do. Some people scan the business cards they receive using cloud-based services such as Cloud Contacts. If it works for you, do it. I don't.
Read the analysis and coverage of the conference by thought leaders and bloggers i.e. do read what I write :-). Compare and contrast your views. Comment on their blogs and tweets and continue interacting with them. Even better, create a Storify of what you liked the most. Use delicious to tag all the research material that you went through. Share your delicious tags on Twitter and let people add to it.