The first thing is trust!! Trust is a fragile thing, and once it's lost it's hard (if not impossible) to get back! So how do you create this trust? You have to be sincere and reliable!! When you're talking to someone, LOOK AT THEM! If you say you will do something, DO IT! What did your mom tell you when you were growing up? "You only have one chance to make a good first impression!" Mom was right!!
The second thing is commitment!! Building a strong network of really great contacts is hard work! It takes time! It takes LOTS of time! But if you stick to it and you don't quit, over time you'll meet and get to know hundreds of people that can and will help you in your career! You should look at networking like maintaining your health; like we do either perfectly! Networking works best if you do a little bit each day!