Sometimes you don't know what you want, or how to say it.
When that happens to me, I just sit in a quiet place, close my eyes, and try to open my heart. My Higher Power knows what I need even when I can't express it. Sometimes that is enough. Part meditation, part prayer I guess. Often when I quiet myself, my true needs come to the surface and then I can put something together if I need to say it in words.
I don't think prayer has to be words, though. You could draw a picture, or write a poem, burn a candle with good wishes attached, watch the sunrise with strong cup of tea. I think all those things can be prayer.