You need to accurately record search strategies so it is best to write up searches as you do them. Best practice is to record searches complete with results numbers so that it is very clear exactly how many results are found by each line of the strategy. Because articles are constantly being written and indexed, it is important to record the date of your search.
Register yourself with databases and log in so that you can access your search history, combine search lines, and save your searches. You can also export searches for later use.
Once your searches are saved you may find it useful to set up alerts to notify you when any new papers relevant to your review are added to the resource you are searching. You can also easily run and update searches at a later date if needed.