A few years ago I leased a claim from the BC Gov on the Fraser River in central BC. It was fun, but I still have my desk job. Probably the most important thing I learned is that you have more success by digging. Dig in the creek, and dig where you think the creek used to flow. Gold is the heaviest thing in the creek and has been settling for centuries. Dig a hole and pan that stuff.
Also, don't be gentle on your panning. If there is gold in that pan it is going to be very hard for it to climb the sides of the pan and fall out. Be aggressive to get all the crap out fast and you will process more material.
Oh and last thing - hunched down in a creek panning sucks. If there is gold there get a little sluice box asap. I had a metal shop bend me up some alum into a trough, I put adjustable legs on it and lined it with black floor runner material that had grooves. Worked really well.