Talk to someone about your topic and as you're talking, have them record the who, what, when, where, why and how of your topic. All of the things they write down can potentially become search terms for you.
Brainstorming keywords can save time when trying to perform search. For example, the topic of reasons why people do or don't seek help will be easier to explore if you stop and speculate on what some of the reasons may be.
Although it's a cliche, think outside the box. Are other types of advocacy groups doing something innovative that could be incorporated into this arena?