Before launching into the search engine optimisation process, take time to work out what keywords are important for your charity.
Brainstorm the important keywords for your charity. For example, if you are a disability charity based in Hertfordshire that wants to bring on new volunteers and raise funds, your list may include the following keywords:
disability charity Hertfordshire
disabled charity Hertfordshire
disabled charities Hertfordshire
volunteer disabled charity
donate disabled charity
As well as thinking of specific keywords, make sure you think of synonyms, spelling variations, plural versions and different verb tenses of your keywords.
For example, if your charity provides sheltered housing, think about all the synonyms of housing, and include alternative spellings of accommodation as it is commonly misspelled eg. accomodation, acommodation. The Oxford Dictionary provides a list of commonly misspelled words.
If you're running short of ideas on keywords, try Google's Keyword Tool. Type in 'disability charity' and click on search. When the results page comes up, click on the 'Global Monthly Searches' header to sort the list by number of searches made - this will allow you to see the most popular keywords associated with the phrase.