Everything has to be done as to let them make the choice to contact you. DWA and a few others are correct, you have to go to an area often and let them come to you.
I had that advice from a few friends over 2 years ago and now I try and just go camp and have a good time enjoying nature. I spend time walking during the day and even at night down a few of the trails. I always try and talk "to them" and show total respect. It feels a little weird at first talking to the "trees" and telling them your only there to be friends and learn, but that is what we started doing. They have to KNOW you mean no harm to them or their family members. Some people try baiting or gifting, I more or less just keep my eyes and ears open. Using some good digital recorders and a parabolic dish with head phones and become invaluable to me. I have heard bi-pedal walking almost very trip out and have had them come into our camp at night while we are sleeping. So far, we have had numerous sightings, tracks in and around camp and a great deal of other activity. Take a look at my journal entry for my total ride and learning experience with them since 2008/2009.
http://bigfootforums.com/index.php/topic/307-my-journal-of-encounters-in-ga/#entry1810
TOTAL Respect and letting them have full control of when they want to connect is the key. Also, as far as yelling, playing recordings of possible BF vocals and anything like that is NOT advised. Tree knocks seem to be fine, but the fact of the matter is you really don't have any idea what your "telling" them when you do that. I used to do all of that too, with minimal success. Now, I have been able to not only have success with activity, but have been able to share this with others.
Good Luck!
KB