There are many theories on the retrieve and here is where I think most people miss the fish. I often see people cast and then reel the lure straight in. Spin fishing is a lot like fly fishing in that you are trying to mimic the bait. Which makes that type of retrieve even more baffling. Baitfish rarely swim straight and in a line like that. They are not all one speed but more a buch of quick, short moves. They are always darting left and right. Predator fish, which is what we are after, are more likely to attack a wounded fish just like the coyote is more likely to take down the wounded or straggling deer. Less energy is expended this way. Because of this you should make the lure swim like a wounded minnow. When you retrieve give the rod a tug every now and then to make the lure dart to the side, then let it flutter down a little before swimming it forward a little and doing it all over again. Change speeds and you will see that the lure reacts different. Practice your retrieve, and watch the lure. See its reaction to your motions and get to know what works best. A little practice and wham! Remember that the lure will react different in the fast current and adjust your retrieve. I have already stated that fishing is different for everyone and this is but one way of many. I vary my retrieve often but always try to make it seem lifelike. Fish are smart, and you have to respect their instincts. Use their predator instincts against them and catch more fish!
The fish often will hang in the slack water just off a waterfall or the edges of a riffle. Rocks and other structure are sure to be hiding baitfish or giving shade and shelter to some of the bigger fish. Try casting upstream and bringing your lure right in front of where the fish are hiding. Jig it along and try to show some flash. The fish may think it is a wounded baitfish and race out hit it. Be ready but don't yank it too quick before they get hold of it.
The fish are very different in each season and methods that catch fish in april, may get you skunked in september. Ignore this fact and you will catch a lot less fish. I think if you are a worm fisherman, with a hook and split shot, this may not apply to you. However, if you are spinfishing you have to mimic what is happening in the body of water that you are fishing. Early spring you are using the tiny gold and silver lures, but mid summer they may not even look at these. Then you need to know what changes to make to put fish on your line. You will also need to remember about water temperature. Trout that sat at the base of the roaring falls, have now moved out in search of colder, deeper, more oxygenated water. You need to make the move with them. A small thermometer will be a great asset. Look for feeder streams and brooks bringing in the colder water and fish there. Run your lures deeper where the fish are likely to be sitting. Shade and structure become more important as the sun beats down and warms the water.