Monitoring analytics on your site, and comparing the traffic your getting now to what you were getting before you started your campaign is a pretty straight forward way to see if it's succeeding. It's hard to judge because SERPs, and almost everything related to your site is going to be delayed to some extent or another. Something you did months ago could just now be benefiting your site, so you have to just work with the available tools you do have and judge for yourself. Checking where your referral traffic is coming from can help determine if your backlinks are driving traffic directly to your site, and looking at your rank for your targeted keywords in SERPs is of course a good indicator of whether or not what's being done is working for you or against you.