Information retrieval begins with defining the research topic or problem. As an information seeker, you will have to clarify to yourself what information you are looking for and where you may be able to find it. When planning your information retrieval, the following research questions may help you define your topic:
After piecing together your topic, consider concepts, terms and words which describe it. Remember the alternatives (synonyms, abbreviations).
Mind maps etc. offer ways of specifying and outlining the research problem. A mind map is a tree-like figure where the topic is divided into sections and further into their subsections.
Look for good search words in thesauri as well. A thesaurus is a list of terms used in databases to give consistent labels to books or articles which describe the same concept. The thesauri vary by databases. So check the one used by each database!
Finto AI suggests subjects for a given text. It's based on Annif, a tool for automated subject indexing.