I really hate replying to these threads because they seem to turn into arguments (especially more recently) but I think this will help. Try this for starters, it is the basic setup that Jos and Monty use most of the time and is a good starting point for most units. I'm much more familiar with HDS units but these settings will work fine with HDI too:
-200khz (this is actually the narrowest cone angle but gives the best resolution of the targets). 83kHz is really intended for deeeeeep water and gives poorer detail but it can be handy at times while searching around over a wider area.
-Noise rejection off
-Surface clarity low
-Colourline should be set at or around 74% (it is in the same menu as sensitivity)
-Colour pallete: pick one of the brighter ones (1 or 13 on the HDS are good but I'm not sure the HDI has the same selections)
-Sensitivity: I run mine on manual all the time and fine tune it constantly but auto does work okay most of the time I guess. You can turn it up or down until you have a clear view of the bottom and targets without a lot of clutter You will need to turn the sensitivity down when running at speed or your screen will just fill up with clutter. If you are getting clutter at really low speeds with either your main or kicker but not both, it is likely that you're getting bubbles and cavitation from the prop and you made need to relocate your transducer.
-Fish ID OFF, learn to read the arches and the bait indicators. The fish symbols are very misleading and you can miss a lot of details which you will see once you learn to read the arches. Youtube has tons of videos of how to read the arches and also how to set it up. The fish symbols (or arches for that matter) do not and cannot indicate the position of the fish in your sonar cone. This technology cannot do that. The shape of the arch can indicate if a fish is diving, rising, approaching or going away from the boat but you cannot read left or right, front or back with this type of graphical display.
Once you get it running the way you like it you can start playing with the split-zoom screens, add overlay data (like your water temp, battery voltages, boat speed etc) on your screens but keep it simple until you get more comfortable with it.
I think the H'birds may be more user friendly like some have pointed out but if you learn to use your HDI/HDS effectively I think you will have a superior system with more capabilities.