Remember that abnormal weather conditions can
affect how your modem performs, particularly high winds or damp.
Call your phone company and tell them that you are
using a modem on your line and that you want AGC (automatic gain
control) turned OFF and the gain increased. Make sure that you say
there is nothing wrong with your normal voice communications (if
that is the case), otherwise they will just do a normal line
check.
Disable call waiting on your telephone line. For
most phone companies this means dialling dial #43# on your voice
phone
If you have two phone lines or more in your house,
you may find that they have been installed using a DACS box, which
effectively splits your phone line into two, each of half the
bandwidth. This is fine for voice calls but completely ruins the
speed of an internet connection. If you have more than one phone
line, ask your phone company if they have used a DACS box, and if
they have, enquire about the possibility of having two *full*
phone lines, i.e. two actual cables from your house to your
exchange, instead of a DACS box.