If you watch anime in Japanese at all, one word you may have learned is suki which means "like," usually pronounced quickly so that it sounds like "ski." This compels all students of the language to say sukii ga suki! (I like skiing) as soon as they learn the word since it sounds funny to the ear. The proper usage would be something like watashi wa sushi ga suki desu, literally "as for sushi, I like it," but since the Japanese love to omit words from their sentences, a more common phrase would be just sushi ga suki, "[I] like sushi," since the subject is generally understood. In addition to serving as "like," suki also describes feelings of romantic love, and when someone confesses their feelings for another, suki desu is what they'll probably say. A variation of suki ("like") is dai-suki ("big-like"), usually said by a cute female anime character before they glomp a male character violently in a big bear-hug.
Suki desu is the most common way to confess your love for someone.