Since your core keywords are likely to be competitive, you'll want to identify secondary keywords that will be easier to rank for as well. Your secondary keywords should be based on the core keyword categories you just identified.

However, they're going to be more specific and more niche than your core keywords.
Start by brainstorming different ways to phrase your core categories. For example, "customer acquisition" could be "find more customers" or "how to attract customers". Come up with as many specific keywords as you can think of. There's no right or wrong at this point, so just expand your categories as much as possible.

Now, it's time to weed out the keywords you've brainstormed that aren't worth your time. Use Google's Keyword Tool to search for each of the secondary keywords you've come up with. For each, select "Exact Match" under "Match Type" on the left-hand side of the screen.

For each of your keywords, note the level of competition, global monthly searches and local monthly searches. For example, "find more customers" has a medium level of competition, 36 global monthly searches and 22 local monthly searches. That tells us that the keyword has a fair amount of competition and very little traffic, which means it's not a great keyword to target.

On the other hand, "how to attract customers" has a low level of competition, 590 global monthly searches and 140 local monthly searches. With low competition and a fair amount of search volume, it's a great secondary keyword to target.

Once you've been through your own secondary list and cut out any keywords that don't make sense, use the same tool to help you find other potential keywords. This time, pay attention to the "Keyword Ideas" that appear below the "Exact Match" you were working with before. Run your remaining secondary keywords through the process again. Identify and note any keyword ideas that are low competition with high search volume.

Finally, select all three match types (using the menu to the left of the screen) and enter your core keywords. Scroll through the list of keyword ideas and pick out any qualified keywords based on the competition and search volume criteria.

Now you have a solid list filled with core, highly competitive keywords and secondary, niche keywords. Since your secondary keywords are based on your core keywords, their success will help support your long-term goal of ranking well for your core keywords.

As Tom Schmitz recommends, keep your keywords organized in a master spreadsheet. Sort the keywords by number of words and then by number of searches. Automatically keep any keywords that are under three words or embedded in larger phrases.

Set a search limit based on your traffic level (i.e. high traffic blogs can handle high traffic keywords). Any keywords that fall outside of this sorting system need to be evaluated for converting power individually.

Use the resource attached to help get you started.