Even the best fitting boot will not give maximum performance unless it is correctly laced up. Correct lacing ensures that boot fits snugly and will prevent 'forward slip' of the foot in the boot and will reduce friction that could otherwise lead to blisters. When lacing the boot ensure that you start from the toe and gradually tension the lace between each set of hooks. Lace locks allow for the tension to be held over the fore foot whist giving a separate level of adjustment and tension around the ankle of the boot.
Be prepared to adjust your lacing as you go. It is common to find that as you need to re-tension the lacing after a short distance even in boots that have been well broken-in. Also the foot shape will adjust during the day with temperature, terrain and load carried.