You should be documenting your search as you go along - this is your search methodology. Keep a note of the following:

- Which databases/sources you chose and why.

- Which search terms you used - including different strategies for different databases - it is common to actually replicate the searches.

- Your inclusion and exclusion criteria.

- Numbers of results at each stage including before and after handsearching.

How long should my search methodology be?

It varies! For articles, it is usual to summarise to "We searched X databases for X concepts....", however for systematic reviews you will be expected to account for each part of your search process.

For some examples, see Appendix 3 of the Centre for Research Disseminations's guidance here. (on p249)