I'd like to support what dguyton has said about recording yourself. It's so hard to pick up little problems and issues with your sound when you're concentrating on playing and singing and what's coming up on the chart and is that danged Bm on this line or the next. But when you listen to yourself, it's a lot easier to pick up on things like your voice dropping off at the end of each line or that you throw in extra strums in a certain transition and throw off the timing or all sorts of things like that.
When I first recorded myself singing, I was astounded at how poorly it came out. I like Russell Harding's voice, and so sent him a copy of the recording asking for any advice. He gave good advice, and I also used some on-line lessons, recording myself doing the same songs over time. Now this past weekend, Topdown gave me an unsolicited complement on my voice, which was nice to hear. Recording, listening for errors, being constructively critical of yourself and getting the advice of people whom you respect will take the place in some small way for having the immediate feedback of a live instructor.
dguyton also gave some other excellent advice in doing what you want to do eventually slowly and accurately and keeping time now, and by the time you've done it 1,000 times a dozen times a day over the course of months, it's going to be smooth and accurate at any speed.
The only criticism I have of his message is the suggestion that B is possible by anyone other than a mutant.
Granted B chord amnesty by King of the Mutants (Long live the king).
If it comes from the heart and you add a few beers... it'll be awesome! - Mekidsmom
When in doubt ... hats. - B.G. Dude