Lighting, lighting, lighting. The same boring scene at noon can be fantastic at 5:00. Filters are also very useful: even with a phone, you can hold a filter (e.g. a circular polarizer) in front of your lens and sometimes get good results. The composition suggestions folks have given are also good, but you don’t necessarily need a complex, multilayer scene to create a good image - however, even a complex scene may not help you if the lighting is too poor.
Flickr, even now.