Aside from punk rock being as simple as 3 chords and an 8 to 16 beat feel theres a bit more to making yourself apealing to....dare i say fans? If you are not determined for one you'll not be going anywhere special and for a second note, be a stage icon. Most people will think that it's selfish or crude to take up the stage by going wild but I would almost call them stupid. There are so many people out there who by watching he energy will only then begin to hear it, so take a note, turn off thier tunnel vision.
Afraid of singing? Dont be. There are many people I know who when they sing I wanna just shut them up, but thats not because thier singings bad, its because they talk with the beat instead. Everone can sing, but not every one sees how. Heres a tip, when you sing, sing loudly, and when you feel the words in your chest instead of your mouth, then your singing.
Now putting a song together this is much easier said than done I know. Music first, for god's sake music first before lyrics. Writing some awsome lyrics is great but really when you try to make your music match your lyrics youll find that you just dont catch the same tune as your voice or feel of your expected flow. This is a major no no. Now what you should do is, pick oh say... 2 power chords and one regular chord say Em. Now play these in the desired order and beat and so and so, now, take the frets that youv played everything on (you should definately stay on the same frets!) just fiddle around with the seperate string on these frets until it somewhat follows or alternates the flow of your last riff this can be a mid riff between chorus's or an intro or an outro. Youll be amazed when you find that you should just sing about someting funny or contradictions or anything that comes to mind and always write it in the tune of your riffs and youll shit yourself on how much easier this will be.