Part 1: "I love you" in Japanese
One of the most popular phrases in any language is probably "I love you." In Japanese, "love" is "ai （愛）," and the verb form "to love" is "aisuru （愛する）." "I love you" can be literally translated as "aishite imasu （愛しています）". "Aishiteru （愛してる）," "aishiteru yo （愛してるよ）" or "aishiteru wa (愛してるわ, female speech)" is normally used in conversation. However, the Japanese don't say "I love you" as often as Western people do, because of cultural differences. I am not surprised if some Japanese say that they have never used these expressions in their life.
The Japanese generally don't express their love openly. They believe that love can be expressed by manners. When they put their feelings into words, it is preferred to use the phrase "suki desu （好きです）". It literally means, "to like." "Suki da （好きだ）," "suki dayo" (好きだよ, male speech) or "suki yo (好きよ, female speech)" are more colloquial expressions. There are many variations of this phrase, including regional dialects (hogen). "Suki yanen （好きやねん）" is one of the versions in Kansai-ben (the Kansai dialect). Since the phrase can also mean "I love it," and because of the popularity of Kansai-ben, it is used as the name of an instant noodle soup product (See the picture below).
If you like somebody or something very much, "dai (literally means, big)" can be added as the prefix, and say "daisuki desu （大好きです）."
There is another word to describe "love" which is "koi（恋）." The kanji character for "kokoro (心, heart)" is included as part of both kanji characters. Compare the kanji characters below (From left "kokoro," "ai" and "koi").
Both "ai （愛）" and "koi（恋）" can roughly be translated as "love" in English. However, they have a slightly different nuance.