If you've performed the Trace Bitmap feature, you may discover that you have various vectors based on colors. It can be confusing enough with a single color trace. Check to ensure that they are ungrouped (control-shift-g) to allow you to attack each vector independently.
Select a vector trace and set the fill to none and set the stroke to the desired color. Check the thickness and set it to as thin as you can see. This will help you distinguish between various vectors more easily.
You should also place these vectors on a layer separate from the image layer. That will allow you to change the transparency of the image to a lower value, making it lighter and in the background. I've found this allows for a more easily adjusted vector.
Additionally, you can place each vector on its own layer and use the tiny eyeball to blink a layer out or in as needed.
It's difficult to determine what else would be helpful without more information.