Setup Problem #5
No GDOP (Geometric Dilution of Precision) on the GPS's main screen.
GDOP tells you the spacing of the satellites and the resulting accuracy of your fix. (Generally speaking, the lower the number, the better: One is considered good; three or higher means you shouldn't place much faith in your fix.) On most units, GDOP is buried deep in the menus - and on some units you can view it. Truth be told, modern GPS is so darn good that you may not ever need to question its accuracy. But unintentional jamming, solar flares and bad fixes do happen occasionally, and you'll sure want to know about it - and having GDOP front and center can save the day.
If your unit allows, add a data box with your GDOP data inside. In many cases, however, this won't be possible. Instead, you'll have to figure out how to get to the GDOP in your unit's menu and memorize the path. Then if you ever grow suspicious or something seems amiss, you'll know how to check the accuracy of your fix quickly.