I'm still learning my sonar units. Well I know the Piranaha Max 220 pretty well. However I am still learning all the features on my 899SI. I too won't fish a spot unless I mark fish, and then sometimes I still won't fish that spot. Usually because its looks to be the wrong species of fish. I haven't mastered the look of fish on some cover yet, and may still fish it to confirm that there are no fish there. While fishing I will mark spots that look good for another time of the season. Like deep brush/trees for summer months, or brush/trees in transition areas during the migrations. Then come back and fish them. I try to spend an hour or so looking for new spots. Recently I had the thought to use that hour to search for spots that would be productive during the next crappie season. This time of year I should be looking for some deep water to shallow water transition routes. If they haven't started moving, they will be soon.