That's a tough one, and it depends entirely on the style of the project you are working on. The timing is going to be very different between Davy Jones jumping vs. Mr. Incredible jumping vs. Horton jumping. These projects all land at different places on the meter of stylization, and each of those character's movements and timings are dictated heavily by those chosen styles.
If you're working on a more stylized piece, and are creating a performance that you can't find or create reference for in the real world, then my advice would be to use the principle of exaggeration to push the timing and poses that you see in the real world.
You always want to base your animation on the real world while adhering to the rules of the universe that have been set up by the style of the project you are working on. No matter how stylized the motion, if it has zero connection to the world we live in, the audience is going to have a hard time connecting to it, and will likely find it confusing or off-putting. You want to give the audience some anchors - something they are familiar with, and use that as the jumping off point for your stylizations.
As an example, let's say that you are animating a character jumping up into the air, but you want to give them extra "cartoony" hang-time. In this instance, I'd encourage you to study (and maybe even film) the mechanics of how a real jump works. Jump around at your desk and feel what happens in your own body. Study how the whole body squashes on the anticipation, stretches on the launch, squashes at the top of the jump, stretches on the way back down, and squashes on the landing. Just study ALL that stuff about how a real jump works.
Once you know how a real jump works, now you're ready to animate your exaggerated jump. Just take what you've observed and apply your knowledge of the principles of animation to it (including and especially exaggeration, in this case) and you'll be fine! Keep that overall squash and stretch for at least the launch and landing as anchors, for example, and be sure to have a frame where at least one toe is still on the ground with a very straight leg so the character feels like he's pushing himself upward. Maybe get his arms involved, as people do, etc.
With those anchors in there, you will successfully communicate the idea of a jump, no matter what other craziness you now add to the mix. Give him a longer hang time, for example, but try to hang onto those anchors as well. Keeping him on a nice arc would probably be another good anchor, to keep things somewhat rooted in the way the audience understands how our gravity works, but that doesn't mean you can't elongate that arc and keep him in the air for as long as you possibly want to!
Hope that helps! Have fun, and keep animating!