There are various types of irrigation systems on the market. For general flower-beds I prefer a system such as this drip-fed irrigation system recently installed for a client in NW London. It basically acts like a very clever hose! Once laid out and assembled, the pipes can be buried just under the surface, meaning less evaporation as the water will soak into the ground where the plant roots are.
The system can also be linked to a timer, making it ideal for holidays as well as daily use. A system like this can save you quite a bit of time and effort if you are looking for a low maintenance garden, and doesn’t cost as much as you’d think.