The more parameters you select, the fewer results you are likely to get. As a general rule, if two or more levels of specificity are offered for a category, only use one of them. (For example, don't select a gender and an associated individual.) As another general rule, the more (and more specific) options are available in a category, the less useful it will be to add other search parameters. For example, the categories of Find Site, Current Location (Site), and Associated Individual are best used all by themselves since they will already narrow down the results to a very small number.
A planned future feature will be for the multi-level parameters to dynamically change what is offered at the next level. For example, if you select the region "Scandinavia", the "Find Sites" menu will then be restricted to sites in Scandinavia.
At the beginning of your search results report, you'll be told how many records matched your search. If you want to revise your existing search, just use the back arrow to return to the search page and your previous selections will still be there. If you want to clear your selections, use the "clear" button.