If you are able to write down the templates, but then get stuck figuring out what to do next, try asking yourself the following questions:
What do I need to know about the first of the list or the current person?
For example, if we are counting blue-eyed people, you will need to know if the person has blue eyes. If we are gathering names of CDs by a given artist, you will need to know whether the CD is written by that artist. Figure out what you need, and write down the code.
Is what I need to know a question? If so, insert a cond.
"Does the person have blue eyes" is a question, so we'll need a cond. In contrast, "the number of copies in stock for this CD" is not a question, so the cond might not be necessary.
What kind of data is the output? A number, boolean, list, etc?
You can find this by looking at the contract and test cases.
What operator is appropriate for the output?
After this, all that remains is to pull the pieces together.