Placing links within post content is probably one of the safer routes to go when commencing a link campaign. For one the content will attract clicks, secondly the link will be keyword focused traffic. It’s a much slower way of building “natural” looking links and it will take some time and dedication but the rewards are definitely worth the trouble. Of course this requires a bit of quality on the part of the writer and good writers are hard to find. Don’t equate a good writer and a good blogger. They are both different animals.
Buying run of site links can be successful in limited quantities. Having a well placed link on a trusted site on the blogroll can push traffic to your site. However having too many run of site links creates a large influx of inlinks has often raises the red flag with the Google police. When a site all of a sudden gets a ton of inlinks that’s not natural and a Google engineer is going to take a closer look at where the links are coming from. Buying links isn’t wrong … so long as your buying them from Google. Just be careful. You don’t want your link count to jump from 100 to 10,000.