ive read that i need to search a phrase, and then search the phrase with quotes around it, and if the phrase has a huge search without quotes, and very small with quotes, its gold? or am i way off? also, i search a phrase, and sort the results by reverse advertiser competition, and pick one that has a lot of global search volume and a low advertiser competition? what is a good number for global search volume? 5000 enough to make it worthwhile?