The most important factors to consider when picking a trekking boot are the fit, ankle support, water proofing, and stiffness.
The most important factors to consider when picking a trekking boot are the fit, ankle support, water proofing, and stiffness.  Make sure that you are comfortable with the fit of your boot and that you have broken them in well before your trip.  Do NOT show up on a trip with a new pair of boots!  Likewise, do not show up on a trip with a boots that are completely worn and falling apart.  Never compromise with footwear on a multi-day trek!