I've been playing around with my Lowrance some lately trying to really learn how to use the unit. I have an LCX-17M but a lot of this stuff is the same between the newer units. I made myself a cheat sheet and figured it might be useful to post it here. This is all taken from the manual.

I also have a question for any Lowrance experts out there...
There are two ways to mark a spot on the GPS. One is using an icon (hit enter, then select the icon). The other way it using a waypoint (hit wpt and add it). I made the mistake of marking everything on my GPS so far as icons. I can get back to these places generally no problem. The tricky part comes when you mark several things in close proximity as icons, you can't name them. So when you go back later you can't tell which one is which. Waypoints can be named and navigated to using the navigation functions of the GPS.

So basically, I'd like to convert icons to waypoints. Anyone know if its possible?

Here's the cheat sheet. Additions or corrections are welcome :)

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Sonar Operations
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Sonar Chart Mode (greyscale, reverse greyscale, black bottom, etc)
Sonar Page -> Menu -> Sonar Features -> Sonar Chart Mode

Stop Chart (turn of pinging of transducer presumably)
Menu -> Stop Chart

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GPS Operations
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Copy Coordinates from internal memory to MMC card
Menu -> System Setup -> Transfer my data
It will then prompt 'transfer data which way'
Answer Save to save to the MMC Card
Rename the file if desired

Copy Coordinates from MMC card to internal memory
Same as above except save to internal memory
There may be multiple files on the MMC card so pick as needed

How to erase trails
Menu -> My trails
delete all

How to save a new trail, from the top
To generate a new trail go to Menu -> My trails
Select the current trail and hit enter
hit right arrow and then deselect active
that will deactivate the trail and cause it to start making a new trail
When done creating the trail, deactivate it using same procedure as above

How to view trails
Go to Menu -> My trails
select the trail to view and right arrow then select visible
same can be used in reverse to hide a trail

Navigating a trail
Menu -> My trails
Select trail to navigate and hit enter
arrow over to navigate and hit enter or use reverse button to navigate trail in opposite direction as it was recorded

Create a waypoint from coordinates (enter a waypoint manually)
Hit WPT to subcategory column then hit New
Press Entered Position then Create
Press Latitude then enter latitude
Press Longitude and enter longitude

Navigate to a Waypoint
Hit WPT -> Saved then enter
to look for the nearest, press to nearest
or look by name through the list
or use find by name

How to edit a Waypoint's Properties
Hit WPT -> ENT -> ENT -> ENT
go down to the waypoints name and select it by hitting Enter
Go down to edit waypoint and hit enter again
You can rename the waypoint, edit the icon or view the coordinates for the waypoint

Navigate to an Icon
Use arrow keys to place cursor over Icon
Press Menu -> Enter to navigate to cursor

Man overboard
Press zoom in and zoom out at the same time
Go to chart or map view to navigate to man overboard point

Set an Alarm Clock
Menu -> Timers -> Alarm Clock

Change Coordinate System (change from degrees to decimal)
Menu -> GPS Setup -> Coordinate System

Map Detail Level
Menu -> Map Data

Show Lat/Long grid lines (could be useful to compare to fish-n-maps with GPS waypoints marked)
Menu -> Map data

Map Orientation
Default is to always show map to true north which can be confusing
To change hit Menu -> Map Orientation
'Track Up' rotates as you rotate - probably the most useful view
Course up aligns to the the direction you are currently navigating to (assuming you are navigating somewhere)

Adjust Contrast of the Screen
Menu -> Screen -> then adjust the slider bar for contrast

Turn off Annoying WAAS Alarm
Every time you turn it on it gives you a WAAS aquired message
To turn it off go to Menu -> GPS Setup -> Show WAAS alarm and disable it