When you mine with P2POOL I can takes some time before having any results (depends of the coin and traffic). When you get share it will give you more part when the pool find a block. You will get paid only if the pool find a block. If it is not clear enough you can have a look on my site. I have developed a small interface that is showing the bloc on the current miners payout it is fun an really more easy to understand. Just have a look at the FAQ at
http://litecoin.p2pool-mining.org/stats/200 for more info. You may want also to try it.