As an advertiser, you know that pay-per-click campaigns take a lot of trial and error. You set up your keywords, write your ads and track conversions until you find just the right combination that works the best.
You COULD use a keyword research tool. That would allow you to see exactly what your competitiors are doing, so you can "cash in" on their "test" and launch with the most lucrative combinations possible.
To keep growing your business one of the key elements is to know what is going on in the market, know what other people are doing is something that you need to know, then have a tool which make this process automatic, is fundamental because doing it manualy is too time consuming.
DO NOT go and dump in a gazillion keywords into your adgroups and campaigns- unless you want to boast about how many terms are in your keyword portfolio. The majority of these terms, scored by whatever techniques are going to be junky and low volume- and the engines will penalize you for it. Rather, what I do is hand pick just a few terms per ad group and then borrow ads from competitors that are already bidding on those terms. Sounds simplistic? Well, it is- but it works. Make sure you group your keywords tightly, so they all reflect the same user intent. The engines will choose one of the ads from that ad group to show, so make sure that each keyword is just as relevant for the ad you show.
You'll also want to look at your analytics data to get a sense of quality- don't be just a PPC tool jockey. Check out your landing page bounce rate per keyword. You'll find that some terms will have a 60%+ bounce rate and should therefore either be cut- or you have to change your landing page. A bounce rate is what percentage of folks bail on your landing page. Most affiliates choose to look only at conversion rate, but bounce rate is a great intermediate metric, since you get a lot more data earlier than having to wait for a conversion.
By the way, if you aren't using AdWords Editor and are trying to optimize via the web interface, you are handicapped right there because you can't make bulk changes and do "Excel-like" things like sorting, find/replace, and copying.
PPC, article writing, and youtube is my recipe for not working a W2 job.