For me, sometimes it's best to not try to write anything, and just let an emotion, thought, or feeling hit me. It can start with a random word, scene or thought, and I'll tap into the emotion behind it to build off of it. I'll start thinking about the emotion behind the thought, then let it write itself. If it's a poem, I'll think of what the initial concept means to me, and then let it write itself as I conceptualize the image. Feel, color(s). From the image, the sounds come and rhyme/off rhyme sequence(s) as well as pace.
Other times, it's just best to stop trying so hard and let the writing build itself inside of you. There are times I'll get a random thought, and I'll think "hmm, that's interesting" or I'll have a concept that really hits me. But for whatever reason, I can't connect the dots beyond the initial feeling. In those times I just keep it in mind, walk away and let it breathe. Think about it time to time, write the initial thought down and then walk away from it. Pray about it, then when I have a little more write that down. Repeating that process, write, pray/think on it, walk away, write. In the process, asking myself and talking to God, what does this mean to me? And how can I convey it to/for others? Where does the reader fall into this, and how can I bridge this to them? Also, don't be afraid to jump around. Sometimes you can get seemingly completely different ideas but once you step back you can find a bridge to bring them together.
Then there are the times where I just have to write it out like others have said. Think about the character and who they are. What makes them a person/unpersonable. What's their quirks? What's their color? What do you want the world to know, and how directly/indirectly? What makes them, them? Music, age, interests, thought process, reader/non-reader, how do they relate to you? You to them? What are some things in our world that have effected you? How in turn does it effect them? Where can the reader fall into them, what makes them multi-dimensional?
Other times, the best way to write is to read and study others. Read others works and think about how it compares to your own style. How would you write this scene? Or how does this poet's strengths relate to your own? What made them write about this? What is/was their thought process? How would I write about it? What do I feel, what emotion/thought(s)? Study the writer's background as well.
One 'exercise' I have is basically staring at a blank sheet of paper, and again tapping into my feelings. Asking myself, how should the paper be filled up. What am I feeling today, why do I feel it? What image, picture, word can explain it? Then what scene, etc.
One final thing I'd suggest is rest in the fact that you have a God-given talent. Don't allow yourself to be overwhelmed but rest in Him. Don't be afraid to walk away, because a lot of times what you have to say will find you. It will rise up in your heart, and you'll have to write down what it's saying. Let who you are in Christ minister to yourself and then turn around and give it to your reader. Trust that the Lord will give you something to say, stay in prayer, and let it write itself. Turn to your source and let Him work.
Praying for you and all my fellow writers. I hope this helps. I echoed a lot of what others have said, but that's what helps me.