Try putting your search criteria in speech marks, e.g. "first jhana" rather than just writing: first jhana, which brings up shitloads more, largely irrelevant, threads. This is what works for me, but I did find the search function annoying for a while since there's no instructions or tips on using wildcards or brackets to refine your search.
Bagpuss, I hadn't even thought of that but it's a good method and can also be combined with the "search criteria" to refine the results further.
