[l0nEr]

Hey, im new to the forum. Just wanted to ask a question. When do they use katakana or hiragana. Is it ok to just switch from hiragana to katakana?

Its like, for example, i found this in the lyrics in the KAT-TUN song, REAL FACE. "このナミダ・ナゲキ→未来へのステップ" . Why is the ナミダ written in Katakana? Does it still mean the same as the なみだ or 涙? Also, i think Orange Range Sayonara is marketed in Katakana too? instead of Hiragana?

Why is this so? Thanks a lot.