To create a customised homepage copy your index.php file and call it home.php. WordPress will use home.php for the home page of your site if it finds one, otherwise it will use index.php (there is also a more complicated way by changing settings).
Showing posts from a specific category on the homepage
Add this before the loop
<?php query_posts('cat=2&showposts='.get_option('posts_per_page')); /*SPECIAL - ADDED TO ONLY SHOW POSTS FROM 1 CATEGORY ON HOMEPAGE*/ ?>
Feel free to comment if you can add help to this page or point out issues and solutions you have found. I do not provide support on this site, if you need help with a problem head over to stack overflow.