What happens when you request to be qualified for a hit? How do you know if it's a yes or no? Do you receive an email? Or their hits just open up to you on the dashboard?
It varies, depending on the qualification. If you mean the ones that you click on a HIT you don't qualify, those don't really go anywhere. I don't even know if the requester gets the requests. I've almost never gotten a qualification that way. But the ones that are in the HITs themselves inviting you to take it for future studies with the words "qualify/qualification" in the HITs then sometimes you will get an email with the qualification, but most of the time you will just see it open up on Mturk without notification. Just keep checking.
also, if it says in the hit to 'take a test' then take the test and if you pass the test, the hit should open up for you too. Be sure to get as many qualifications as you can. You never know what will turn out to be a good one.
Sometimes those tests will actually tell you if you passed or not by giving you a score or number needed to pass. There has been plenty that I failed in. Life goes on and there's always others to try.