The regular leaves won't do shit unless you smoke a ton really quickly, you want this stuff called Purple Sticky Salvia and you'll find it at some head shops, the 10x extract of that is supposedly equivalent to a normal 20x extract, and in my experience it's true. Load up a bong, take a huge rip and hold it! hold it for as long as you can, let it out and take another rip immediately!
As CannaBoss said it's like a cartoon world to some people, others just get visuals like acid or shrooms, taken in high doses it's similar to ketamine trips where you're existing in another world temporarily. One of my friends thought that a lamp in my house was telling jokes and couldn't stop laughing.
The trips last anywhere from 2 minutes to 30 minutes depending on the dose and the person, even after the trip is over you still feel awkward for a little while. Most people will agree that once you take a hit of salvia you won't want to smoke anything else for a little while as everything else you smoke will taste like salvia + shit, also feel like there skin gets hot for a few minutes.
So:
-Get at least the 10x extract (Purple Sticky Salvia is recommended)
-Do it in a safe place
-Don't panic