Because keeping garlic and onions in the same immediate area can cause problems with accelerated decay and sprouting, it will be important to store them in separate places so you will not have this problem. Many people choose to put their garlic and onions in different baskets or containers in the kitchen so they can keep them fresh for as long as possible.
It is important that you store your onions in a place that has a fairly regular temperature of around 32 degrees. One of the good things is that garlic can be stored in areas with temperatures that go up as high as 90 degrees, so you will not have to worry about keeping them in an area with a stabilized specific temperature such as with onions.