It might be surprising to discover how doing something that you enjoy can also be a valuable songwriting guide. You have most likely heard a lot of songs, but the next time you hear them, try to concentrate on things you weren't thinking of before. What's causing you to react the way you do to a particular song? If you really like it and you feel moved by it, find out why. Take a look at it closely and take each part separately. Is it the lyrics that drew you in? Or maybe it's the guitar part, or a certain chord they used in the chorus. Listen to each of the background instruments too. By doing this, you'll see all the clever little tricks that have been used, and more importantly, you will understand why they work.
Don't just listen that way to your favorite songs; concentrate on the ones you don't like too. Are the lyrics stupid? Is the melody annoying or not interesting enough? Many times, the songs you don't care for can teach you just as much as the ones you enjoy. They can show you what to avoid so you don't unintentionally fall into the same traps. And then there are the songs that you may not like, but there are still one or two things about them that impress you. Be honest and give credit where credit is due.
The more songs you listen to from the "inside out", the more techniques you will be exposed to, and pick up along the way. This will give you a much greater range of things to work with when you write. Eventually, you will be prepared for virtually every situation you encounter in writing music. When you get to that part where you're not sure what should come next in a song, you will have tons of ideas because of the knowledge you acquired from listening and understanding other songs. Then, songwriting will not only become easier, but it will also be a lot more fun for you. In creativity, the more options you have to work with, the better.
Using the analogy of painting a picture, you can imagine how the artist would be limited if all he/she had to work with were three colors: blue, red, and yellow. They have to create a picture that they know will work with those colors. That means that they can't draw whatever their imagination thinks of. Their imagination is limited to creating things that will only work within the means they have to complete the picture. But if they had more colors, such as purple, orange, and pink, they would have a little more room, and it opens up the possibility of new ideas.
So painters keep building and building their collection of colors until finally they have ones like magenta, teal, cadet blue, and so on. Now, when they get to a part of the painting where they have to use red, they have several options. They don't have to settle for just "red." They now have things like scarlet, crimson, and violet red to choose from. The paintings are really brought to life and they have much more depth to them because the painter can go wherever their imagination takes them.
The things you learn from the songs you listen to are your "colors." You can never have enough different colors or ways to use them. Building your color palette takes time, but the good news is it's also a lot of fun because you'll be doing one of your favorite things: listening to music! So the next time you hear a song, really listen to it. It also helps to keep notes on each song so you can refer back to them. They don't have to be detailed explanations, just short phrases or reminders of what you were thinking of when you listened to it. These notes can also help you deal with writer's block by giving you new ideas to write with in the future.