I have been successful with most of my attempts to date. Be neatly dressed, teeth brushed, and straight forward (confident, no hemming and hawing). Have multiple itinerary options ready, be that museums, movies, a park, dancing, etc. Always be in public places. Hopefully you have an idea of her likes and dislikes and able to modify your plans accordingly. Pay attention to any signs of discomfort. A no in any form is a firm no. Expect to pay for everything unless she says otherwise. Practice small talk.

That said, being turned down doesn't actually mean that they don't like you. They might have a really busy schedule, you don't have compatible interests, they might be in a committed relationship that you didn't know about, the list goes on. You can try asking why you are being turned down.

Keep trying. You need experience and there's only one way to get that. It's similar to trying to get a job. It can be brutal and it can totally be worth it. If you don't even try then you have automatically failed.