Summarize the following:
Physically unplug the phone and the cord from the wall. Go to one of your other phones and check that it has a dial tone. If none of the phones in your house have a dial tone, see the next section. Remove the working phone and it's cord from the jack. Plug the phone that wasn't working into the same jack that the working phone was using. Use the same cord that the non-working phone used. If the phone has a dial tone after being plugged in, then the original wall jack is the culprit. If the phone still doesn't have a dial tone, then the phone itself is likely broken, or the cord isn't working. Before writing off the phone, try the working cord from the phone that did have a dial tone. If this gets your original phone working, then the problem was a faulty cord, which can easily be replaced. If this doesn't work, then you'll need a new phone. If the phone works on the other jack, then the original phone jack is likely faulty. Most carriers will not pay to repair this, which means you'll need to either fix it yourself or pay for a technician to come and check the wiring. See Install a Residential Telephone Jack for a comprehensive guide on replacing and rewiring a phone jack.
Unplug the phone that doesn't work. Find a phone in the house that works. Unplug the working phone and cord. Plug in the phone that wasn't working. Check for a dial tone. Try a different phone cord. Consider repairing the wall jack.