Summarize the following:
Pecans may begin falling from early September to November, and preparing for harvesting should be done prior to the nuts falling, but closely enough to the anticipated fall that your efforts will not have been undone by time and weather. Some pecan trees will produce low-quality nuts, either because of a poor growing season, low quality soil and nutrients, or it is simply a product of a poor genetic background.  Some examples of these contributions to the nut quality are these:  Non hybridized trees produce seedling nuts, often no larger than small oak acorns, with incredibly hard shells which makes obtaining the nutmeats almost impossible.  Other poor genetics can be found even in hybrid trees whose gene pool has passed on poor quality. Poor growing conditions may include a dry spring and summer that did not enable the trees to produce a good crop, especially when irrigation is not used, and in soils that have poor moisture retention to begin with. Low levels of critical soil nutrients, especially nitrogen and trace minerals/elements like zinc, iron, and manganese can substantially reduce the quality of the nuts. Insect infestations such as web worms, bud worms, and pecan weevils can also have a serious impact on the health of the tree and the nut itself. Very late frosts or freezes can damage the blooms and buds of the pecan tree, reducing the set of the nuts during or after the blooming period. In late summer, the pecans will have reached their full size, including their husks, so you should have a good idea of how large the nut will be after the husk dries and falls off.  Note that the husk represents between 25-30% of the total mass of the pecan, so a pecan that appears large while in its husk may still be disappointingly small when the husk is gone. When a substantial portion of the nut's husks have split and opened, it is time to clean beneath the tree.  Raking any debris from bare earth beneath a tree, and possibly taking action to level out the ground may be all that is needed in this situation, but for trees with lawn or pasture grasses, or even weeds beneath the canopy, more work will be needed.

Summary:
Observe the pecan trees for indications the nuts are ready to fall. Establish the fact that the nuts your target tree are bearing are worth the efforts you will put forth. Observe the tree itself for indications of the nut crop, both in quality and quantity. Watch for the husks to begin splitting.