Generally start looking on the downstream side of big rocks and such, the inside of a bend in the stream, any cracks running crossways to the stream bear cleaning out as deep as you can get in them. 

There is a section in the front of the guide on reading a waterway, and where the gold will tend to settle out.  You will generally get black sand with gold, but not all black sand has gold with it.  The stream you were in may not be a producer, see if there is a history of gold coming out of there.

Hope this gets you started.  Try and go out with a chapter member or two, they can be a big help.

Here is a tip as well.

Right now the snow is melting and the rivers are running high, look at the inside curve of a river where calm pools have developed, but also look for newly formed sand bars and dig on the side that has the largest gravel. I found a spot where the river used to run and is now a deposit, but old enough that trees have now grown in, that soil on the rivers edge is rich with deposits.

Think of a river as the wing of an airplane. The top of the wing has the curve which causes the air to flow faster over it, but the bottom of the wing the air is traveling slower. The river is basically no different, look for the calm pools on the bottom of the wing, and best if behind a boulder or tree that is causing a pool to form. If you stick your shovel in and feel nothing but sand either change locations or dig the sand off and dig until you get to gravel.