Jonathan's right, this is really a music question, not a dance question and your best answer will come from someone with musical training. Finding the beats is something I almost never have trouble with because I've been playing music since I was like 5 years old. I don't have any experience trying to teach musical concepts though, so I'm not sure how much help I'll be here. The semi-standard answer is that the 1 beat, the first beat of each bar/measure of music, is typically the strongest beat. "Strong" in music may not have a great, succinct definition, but the 1 beat is often accented meaning it should sound louder than the other beats. Every general rule has its exceptions, but this should be a good starting point. Sometimes beat 3 will also be accented, but not as strongly as the 1 beat (if the music is in 4, that is). I like Jonathan's idea of starting with songs you know and learning to find where the 1 beats are in them. Once you've figured it on on songs you know, you can start listening for it in other songs and with enough practice you should be able to hear it almost all the time.
Counting beats usually isn't too hard to get, though it may take some time and practice if you're not used to it. Other ideas tend to be harder to get, like phrasings and that strong/weak measure idea Jonathan mentioned. I wouldn't worry too much about that in the beginning though. To start with, you just need to be able to count of the measures 1, 2, 3, 4, 1, 2, 3, 4, etc. so that you know where you want to take your steps when dancing. Good luck with it. I'm sure you'll figure it out if you put enough practice into it.
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James Marshall
marshall@astro.umd.edu http://www.astro.umd.edu/~marshall 
