Blog commenting still works, but it's a beaten to death tactic. Some automated programs will generate thouands of blog comments for you, however what used to work really well 2 years will tank your site in no time now. Best thing to, set your google alerts to terms that will bring you traffic. Example, if your a plumbing company that specializes in water heaters set your alerts to new water heater model or updated water heater model. Once you get a few set up the alerts will trigger, now if you get a blog that triggered your alert take a second and comment on it if you can, same for local area blogs, use this technique with g+ and you should see some results.