You can use this tool while searching for ad group ideas or keywords. Keyword planner acts like a workshop that you can use to expand existing network search network campaigns or build new ones. The tool can allow you to search for AdWords tool ideas or keywords, view the performance of a list of keywords, retrieve historic statistics, and develop a new list of keywords by multiplying many keywords lists together. A free keyword planner, AdWords tool can also assist the user in selecting a list of competitive budgets and bids that you can include in your campaigns. You can utilize keyword planner in laying the foundation of a successful online campaign whether you are a highly experienced pro or new to online. All you need is a Google AdWords account and you will be ready to sign in and get on the move.

2) SpyFu: I suggest to have paid account on SpyFu. I just need to find my competitors who using Adwords and review them using this tool. It will show me what ads and keywords they are using. Note that my competitor who paid for that particular keyword knows exactly that it is important for his business including recent trends. Also using SEO feature you can input any URL and find our which keywords they are ranking for.
6. Filters. On the top area of the main pane, you can find the “Filters”. These will allow you to filter your keyword suggestions list in real time. Just start typing and your list will be filtered accordingly. You can filter for “Keywords” (to only show keywords that include a specific word or words); “Suggested Bid” & “Local Searches” allow you to enter minimum or maximum values; “Advertiser Competition” (this comes in handy, because the higher the competition the more money there is to be made if you target that keyword); “Avg. Amazon Reviews” (a neat feature for those who sell products on Amazon or have an Amazon FBA business — less reviews equal less competition, hence more chances to rank on top of Amazon’s product search pages); “Avg. Keyword Competitiveness” or “KC” is Long Tail Pro’s proprietary metric that calculates how hard it is to rank for a keyword in a range from 0 to 100 — 0 being no competition and 100 impossible to rank for. All of these filter columns can be used to sort the keyword suggestion list as you prefer.
3. Finally, there's just good old research through trends and news. Google Trends, keeping up on industry news of the business, and even newsjacking (if there are relevant topics). These all require different resources depending on the business, but once you find the leaders in their news you can not only leverage them for keyword research but also glean insights into how you can become an industry leader yourself (and dominate SEO).
If you’re serious about making a success of blogging, you need a keyword research tool like this. Such tools can also prove useful before you even begin. If you have several ideas, you can do your research up-front, and see which niche gives you the most chance of success, and which is already highly competitive. Working this out can save you an awful lot of time and money in the long run.
Long tail keywords can find people who are later in the buying cycle, and more ready to buy. For example, somebody searching for “tents” is probably early in the buying cycle, just starting to research what they want. Whereas somebody who searches for “North Face Kaiju 4 person tent” already knows what they want, and is more likely to be ready to buy.
In a nutshell, Long Tail Pro helps you quickly find keywords in bulk based on a seed keyword that you input.  In addition to returning hundreds of related keywords, the tool also shows search volume (monthly search volume), advertiser bid, number of words, rank value, and my favorite Keyword Competitiveness (helps you judge the competition and keyword difficulty).