I've found out that having too many links of the same type (like contextual links from articles) makes Google suspicious. THerefore it's very important to have links of different types from different sources, some with anchor text, some with url and some with brand name.
Blog comments? Are they still relevant? Also, what are your goals - getting traffic/link juice/both? For me, it is guest posting all the way, and paid(bought) links all the way.