Just keep writing. I've found the more you write, generally speaking, the better your songs get. At first they're always a little awkward and/or cheesy, but with experience you tend to get better.
As for proper advice, try and think about what you want to tell your listener...as is often the case with me I've been distracted and forgotten where I was going with this...
Singing is largely a case of practise and be prepared to recieve constructive critism. A good, tactful friend is handy there, or perhaps look at finding a music teacher?...
Good luck, hope I've helped some.