You need to find your niche first, second go to Google adwords keywords tool. Type your niche, make it exact match, show average PPC, Average search per month. Look at the results, look for keywords that are a combination of two or three words, for example if your niche is money look for "money making ideas", "online money making", etc. Average search I'd say more than 3000 per month, if you're looking to monetize average PPC I'd say more than one dollar. Looking to get traffic, the keywords that work better are two or three word combination, and average search 3000 or more per month, competition might not be that high. Hope it helps Good luck