Links on your site going to someone else’s or links on other people’s sites coming in to yours?

Links on other people’s sites coming in to yours (inbound links) are more important for rankings provided they are on high quality pages and have good anchor text http://www.seo-blog.com/inbound-links.php

Links on your site going to someone else’s (outbound links) can have a positive or negative effect on your rankings depending on the site (page) you are linking to and also to some extent on how they are implemented on your site http://www.seo-blog.com/outbound-links.php