Paddle wheel to fish finder vs. dashboard speedometer vs. GPS?
GPS! Starting as slow as possible 1.0 - 1.2 mph then increase speed if I'm not getting bit.
If you don't have any of these in your arsenal, there is a device that clamps to the gunwale of your boat that drags in the water overboard to accurately measure your trolling speed. I've looked around to find this indicator and can't find it now. Maybe another member will read this and know what I'm referring to? I've been told that they are very accurate at the slow speeds. Sorry I can't remember.