Find a thread that matches the lace as closely as possible in both color and thickness. Find each loose, broken end and attach a usable length -- about 16 inches -- using a reef or weaver's knot. This will prevent any loose ends from unraveling while you work on another area, and give you a thread to work with to rework missing loops. The neatest mend will result if a lighter weight thread is chosen for those threads that will not be worked into loops, but merely knotted and finished off. This will keep the final mend as delicate as possible.