I don’t know of anyone who has not been in the situation when they know what they want to say but they are unable to produce the word(s). Often it will occur to them later once they are less pressured. This article gives part of the picture.
The more that I am in the field of brain health, the more that I realize that the most important factors in having good memory in an otherwise healthy brain is lifestyle related. The brain needs to be well-rested in order to process, store, and retrieve memories well. Having a calm and focused brain is also essential.
Neurofeedback can help the brain to find appropriate activation levels for good information processing and retrieval. The tips in the article are also helpful.