Step 1: LISTEN!!!Find music that matches your mood. If you are calm, listen to reggae or jazz. If your girlfriend just dumped you, listen to blues. If you are feeling really friggin awesome, listen to metal. The list goes on and on. These are just suggestions. The truth is, you can listen to anything, as long as it inspires you. This first step is crucial for the rest of the process.
Step 2: AnalyzeOnce you have a few songs that inspire your creative process, outline the song structure of each of them. Take note of the rhythm, harmony, and melody used in each part of the song. Is the melody ascending or descending? Is the rhythm played in straight 8th or 16th notes, or is it in a weird 7/8 time signature? Is there a common pattern in the harmony (I like to use the 3rd interval), or is it seemingly random? Outline what is going on with every single instrument in the song.
Step 3: SelectWhat parts of each song inspire you? After outlining and analyzing each song, this part shouldn't be to hard.
Step 4: CopyThat's right. Many of the world's greatest musicians (John Frusciante for example) copied (within reason) from other musicians. Take the parts of the song in the previous step, and try to duplicate their sound.
Step 5: Make It Your OwnThis is the part where you become part of the song. Make small adjustments, until you have something that sounds original, and sounds so great, that you are on the verge of achieving legend status(once you are done with it of course).
Step 6: Clean It UpIt is one thing to have inspiring parts of different songs put together, but it is another thing entirely to make them sound good together. Maybe you can find similarities between song parts. Or maybe, just maybe, you want to use your main riff to blend different parts together. This step takes some practice to get down to perfection.
Step 7: To Be ContinuedLyrics in Pt. 2.