My standard fall back position is that reliable reception starts with the antenna, it location and aim.
The active electronic parts of a good quality tuner should generate relatively little noise... Which means that a consumer grade preamplifier is not likely to improve the overall noise margin of the complete system if 50' or less cable is used to connect the antenna to one TV. So, the following test is useful when trying to decide if an amplifier can improve reception at the TV or not.
http://forum.tvfool.com/showthread.php?t=13646
But, if the antenna, test coax and tuner can not produce reliable reception during the test just mentioned, one needs to be open to the possibility that the antenna may not have the needed gain or directivity, and/or, the location or aim needs to be changed. It's also possible that some source of interference is present... In some cases filters such as FM traps or equivalent devices tuned to other frequency ranges may help... But if the interference is from another station operating on the same frequency, no filter will help because it would also block the desired station's signal.
Once you have proven that you have a reliable signal at the antenna terminals it's time to turn your attention toward getting that signal to the TVs... That task may or may not require the aid of amplification.