The unexpected or multiple bands that you are experiencing in your PCR results, is most likely the result of nonspecific binding or the formation of a primer-dimer. Try the following tips to remedy this issue:

• Avoid excessive cycling as this can increase the chance of nonspecific amplification, for most PCR applications 25-35 cycles is sufficient
• Avoid impurities and contaminates in your PCR components as these can inhibit PCR, and can lead to incorrect amplification
• Avoid long extension times, for most PCR applications an extension time of 1 min/kb is sufficient
• Avoid long annealing times as this can cause spurious priming, for most PCR applications the typical annealing times are 15 to 30 seconds
• Optimize annealing temperature, at low temperatures primers can bind nonspecifically to the template
• Check primer design