maintaining fermenting temperatures

what do most home brewers use to maintain the recommended fermentation temperatures for ales ?

so far i have kept the fermenting barrel in a dark space under the stairs. i like to try and keep the temperature closer to recommended fermenting temp. i see many of these heat belts or pads but these need monitoring to keep the temperature controlled ? so you would have to turn it on , keep checking then turn of again? Or do you plug these in to a temperature control device? I've seen these immersible heaters, like a tropical fish tank style, would these be any better/easier then the heat pads? ( i could imagine a infection issue here maybe ?) do you have a dedicated insulated plywood box where you keep the fermenting bucket in to maintain the temperature? one of the next brews i wish to make is a hefeweizen, and read it's important to keep this around the 17c to get that right flavour. 

thanks