Learn more about SEO in general. Once you have more experience, it becomes easy to buy a BST and reverse engineer it to come up with your own portfolio of high PR places to drop links. Scrapebox is amazing tool for helping you do this too so I recommend watching some of the more advanced training videos on it.
If you just need basic footprints,shailzrocks gave a really good recommendation. But if you want to find the gold nuggets, reverse engineering competitors and services from BST is one of the best ways. Why search for something when you can just follow the trail left by someone who's already found it...