I just purchased my first fish finder (Garmin 300C). The manual does a pretty good job of explaining how to program and activate the settings, but it tells me nothing about WHEN or WHY I should, or want, to use certain settings in a real-life fishing situation. Most of the settings have an "Auto Set" feature, but I would like to have more personal control. Below are listed 8 specific questions on which I am confused and I sure would appreciate any advice you folks could give me. I have the transducer mounted on the transom if that helps. Q1: Setting range of the Depth Scale. Say I am fishing in 30 feet of water. How would you set the Depth Scale and why? What would be the advantage (if any) of setting it manually, rather than just leaving it on Auto. Q2: Setting the Beam Width: The Garmin 300C offers a selection of "Narrow" or "Wide." I understand that the "Wide" lets me view a larger area and "Narrow" lets me view more detail. But I am confused as to when to use one or the other. Example: If I am underway should I use the "Wide" and then switch to "Narrow" to more closely view a certain area? Or should I just leave it on "Narrow" all the time? Q3: It has a zoom feature offering: "No Zoom" or 2x or 4x. It also offers "Bottom Lock." It is the "Bottom Lock" that confuses me most. What does "Bottom Lock" do for me? Why or when would I use it? I am not even sure what it means? Q4: Adjusting Zoom Depth: Does this mean that I zoom only to a certain depth? Say I am in 30 feet of water and only want to zoom to see better whatever is at 15 feet, not all the way to the bottom? When would I want to use this feature? Q5: Depth Line: Manual says: "To reference a specific depth on the screen": Any thoughts on what this does or is for? Q6: Setting the Whiteline: Manual says: The "High" setting "...ALMOST all strong returns are highlighted in white. The LOW setting "... only the STRONGEST returns are highlighted in white. When should I use one or the other? Q7: Sonar Scroll Speed: Here is where I am totally lost. Selections are: Ultrascroll, Fast, Medium, slow (or Auto). I do NOT have a speed-control transducer, so I am assuming that the Auto-- which automatically adjust to the speed of the boat--would be of no use to me at all. Am I correct on that? I am not even sure what the Scroll Speed does or tells me. Any explanations would sure be appreciated. Q8: Fish Symbols: I have been advised to leave this feature Off. What is your advice?