If you need a stronger signal for your "non" smart phones in the house, consider a cell phone booster. And while AT&T, Verizon and others will sell you one of their cell boosters (aka femtocell), we haven't heard many people having success with those. Yes, they are easy to install, but they do not work well in the country.
Living in the rural areas, what you need is a directional antenna installed in the attic or on the roof, with a coax cable that runs into the house to a signal base unit. For about $350, you can boost the cell signal in a 2,500 square-foot house to 4-5 bars.
The cell booster we tested successfully (with Verizon 3G) is the Wilson Electronics DB Pro signal booster kit. The kit includes a directional wide-band yagi and panel Antenna.
Need help setting this up? Hire local handyman, Phil Whitmore, at N-His-Service Handyman (707) 365-5139. You buy the stuff, he hangs it for you.
Finding Your Cell Tower
There are a couple of handy websites that will help you aim and align your cell phone antenna.
CellReception.com Just plug in your city, select your cell phone carrier(s) and aim your cell phone booster antenna in the direction indicated.
OpenSignal.com Similar to above but gives you signal strengths. Aim your antenna toward any signal hot spot (red).