Your first step in buying a motorcycle cover is deciding if you are going to use it indoors or outdoors. If you choose an indoor cover, most can only be used indoors. They provide a nice soft touch to your motorcycle. They do a great job keeping the dust off, but most if not all are not weather resistant or waterproof. Also most indoor covers can not be put on a hot motorcycle. They do not offer the lower heat panels to protect from the exhaust pipes. If you are sure it will only be used indoors your best bet would be the Dowco Duster motorcycle cover. A less expensive and lightweight cover the Dowco StoreAway motorcycle cover should be fine. If you know the motorcycle will be stored outside then an outdoor cover is your best choice. There is a wide choice of outdoor covers including the two best. They are the Dowco WeatherAll Plus or the Nelson-Rigg Defender 2000. Both of these covers offer lifetime warranties and are 100% waterproof. Also both of these covers offer a heat-resistant panel at the bottom so the cover can be put on a hot bike. Dowco also offers the Weather All a lighter weight cover then the weather all plus but with all the same features. For a cruiser type motorcycle you can try the Nelson-Rigg Falcon cruiser cover.
After you have chose what type of cover you need, sizing is next. Motorcycle covers are sized by the make and model of your motorcycle, not how tall or how long it is. When choosing the sizes always go by the application charts. There is a rule however. If you have added any extras i.e.: windshields or saddlebags it is best to go up to the next size. Motorcycle covers are made to fit tight so wind and the elements can not get in. They fit at the longest point of the motorcycle which is at the axles. With this in mind the lower half of your wheels will be exposed. Motorcycle covers are not made to go all the may to the floor. If this is something you want in a cover you should also go up a size. Just remember if you do go up a size it will fit looser on top. Hope this helps in deciding on a cover for you.