Things that can cause disconnects
Rain and wind, especially in the form of our local winter rainy season and storms will cause pops and clicks in your phone line, submerged he line under water, and causes all kinds of speed issues. Bad weather will definitely slow down your connection.
Out of date modem drivers
Many modems are sold with drivers that are already old. Often each individual update to modem drivers (and firmware) tends to be small and incremental, but if you add enough of them together, you can get big improvements in your connection. -> Drivers are also susceptible to file corruption. It is a good idea to keep them up to date to prevent cranky windows problems.
Cheap modems tend to be cheap for a reason. If your modem is in the elcheapo category or it suddenly fails after many years of hard use, it may be time for a new one.
Bad inside wires, Faulty phone jacks and Multiple Devices trying to use the main phone line
There are a wide variety of wiring problems that may be in your house, office or apartment that cause slow connections speeds. Try a new, short phone wire, or a different jack for the phones, or try unplugging the other phones, fax machines, and other devices and see if that improves your connection.
Double check that you are using the right modem driver, updated firmware, and the correct initialization screen
All of these things can be obtained from your modem’s manufacturer.
Try forcing your modem to connect at a slower speed
In your dial up window, put in three commas after the phone number for example
This forces your modem to wait 15 seconds (each comma is about 5 seconds) before attempting to connect. This way the 56K portion of the handshake is skipped and the modem will begin to try to connect at a slightly slower speed.
Ask the Telephone company to test your line
If you are having chronic connection problems, and you have tried all of the above, it may be a good idea to ask the phone company to test your line. Sometimes you can even talk them into cleaning up/conditioning the phone line.