A huge part of songwriting is the artistic aspect, but there are also a few rules you should at least know about. As every other successful musician has done, you must first learn the rules, then follow them, before you can break them. Here are a few basic rules and tips to get you started.
Create a hook
This is one of the most important aspects of a good song. Think of your favorite song. Consider the first part of the song you think of, or the first thing you start to sing. This is probably the hook. The hook is a short part of the song, often a line or so, that is particularly catchy. The hook provides a specific idea for listeners to remember the song by, and when done properly, it's even more than that. The hook is usually the part that gets stuck in everyone's head. In order for your song to be successful, make sure it has a hook.
Use a catchy progression
Chord progressions can sometimes be tricky to write. The best thing to do here is to learn as much as you can about music theory. Pick up a couple of text books or do some research online, whatever works best for you. Theory will help you understand relationships between pitches and chords, and which chords lead to other chords. Once you understand theory, and after some practice, you'll be able to come up with chord progressions on the fly, in real-time. Until then, don't be afraid to borrow what other people are doing. To clarify, it's never ok to steal the exact progression of another song. However, there are numerous progressions that can be found in hundreds, if not thousands of songs. If you can, transcribe the chord progressions of some of your favorite songs. If you can't, look them up online. You'll find that often, the chorus particularly will use a common progression. Pick out one of your favorites and create a new melody for it. Now try the same with the progression from a verse from a different song. Then put them together. Remember, using someone else's melody is illegal, but using a progression that hundreds of artists have used isn't, as long as you mix it up enough that it's not the exact same as an entire song.
Listen to someone else
One of the most important things you can do to become a great song writer is to listen to other great song writers. No one has ever written a great book without reading other books, and no one has ever become a famous painter before seeing any other paintings. Song writing is no different. Whenever you can, listen to artists that you like, and who you want to sound like. Every once in a while, listen to something completely off-the-wall. But most importantly, listen. This is also beneficial if you play the music that you write. If you sing, listen to great singers. If you play piano, listen to great pianists. In music, listening is just as important as writing, playing, or singing, if not more so.
Know the Law
Music law is much too extensive to even begin to go in to here, but make sure that you do some research before attempting to do anything with your music. Breaking music law, whether you knew about it or not, is not a very good way to start a career. The gist is that you can write whatever you want, but as soon as you show it to someone else, you start getting in trouble if any of it is borrowed from anybody else. Even if the work is completely original, it's important to understand how the financial side of the law works so that you earn as much money as possible for your artistic work.