Find Self-Intersections
Create a Feature Line from the object you wish to find self-intersections of (assuming it is not already a Feature Line).
Select the Feature Line and right-click > Copy to Site… (or enter the COPYTOSITE command).
Create a new site under the Destination Site drop-down. This will be used as a temporary site for finding intersections - as such, I usually name it something like Temp.
Enter the FINDSITEOVERLAPS command on the Temp site. This will create an ACAD point at each point the Feature Line intersects itself.
Use these ACAD Points to location self-intersections and fix them.
The feature line can now be safely deleted (leaving the Temp site empty).