Begging for links. Well we've all tried and it is a lot of work for very little return. Have you ever found someone who want to give you an industry specific link, on a site that matches your industry and offers a link with your exact text, on a site with high PR say PR4, 5, 6 or 7? Sites always want something in return. Money or a reciprocal link.   Reciprocal links counter act each other and so don't count at all.  Paying for links as long as it is not detected by google can work but you need to know who you are dealing with and know that they know what they are doing.  Also paying in advance you run the risk of paying a lot for a link that disappears after 2 or 3 weeks.