Lucky Star is one of those cutesy series. It revolves around four best friends who are at high school, and there isn't an in-depth or serious storyline. Each episode has a mini storyline - but the main one is how the four girls get through high school, with their clashing personalities.
My favourite characters are Konata and Kagami. Konata is incredibly nerdy and coooool ;) She is obsessed with video games, anime and manga, and I think she's more tomboyish than her friends. Kagami is a fraternal twin of Tsukasa and she is loud and outgoing.
The series focuses on Konata, Kagami, Tsukasa and Miyuki's friendship, and their random escapades along the way. It's probably one of my favourite animes to date, and I'd recommend it for an easy watch, where you don't have to think, and simply watch for leisure.