Note: You don't have to follow this exactly to a tee to get sub 30--if you do everything optimally you'll actually probably get around a 24 or 23 second time, so there's definitely some room for mistakes. Also note that this only applies to Sandbox Mun Landing, the other categories are longer and much different to this speedrun, and aren't covered in this guide.

Anyways, first, you need to build a rocket which can burn all of it's fuel very fast, while still having a lot of delta-v to be able to get to the Mun as fast as possible. Also, it should optimally be stable at 4x timewarp while burning it's fuel in atmosphere.

Next, you need to figure out when exactly the optimal launch time is so that your rocket doesn't miss the mun. I can't give the exact window, as depending on your rocket design this window will change, so you'll need to test this out yourself before doing runs.

After this testing phase, you can finally launch your rocket and start doing runs for real.

Immediately after burning all your fuel at 4x timewarp you need to slow back down to 1x timewarp just as the rocket exits the atmosphere, to be able to go up to 10,000x timewarp as fast as possible. 100,000x timewarp would be faster, but the Mun's sphere of influence is small enough that the game literally doesn't have enough time to automatically slow down timewarp to 50x before your rocket exits out the other side, so 10,000x timewarp is optimal.

Next, once the rocket gets close to the Mun, start spam-clicking the eva button which appears when hovering your cursor above your kerbals' portrait, so that your kerbal exits their capsule as soon as possible. Make sure that your kerbal does not leave the ladder they are initially put on after getting out. It's also important to note that you do not need to manually slow down timewarp, and sometimes you may need to actually manually increase timewarp to 100x or even 1,000x.

Then, if everything goes perfectly, even though the rest of your rocket explodes, the kerbal should still survive and fall to the Mun's surface without a scratch. This seems to be somewhat random, and as far as I know there's unfortunately no setup or manipulation to consistently make the kerbal survive.

And there you go! Assuming you did everything right, you should have just landed a kerbal on the Mun in under 30 seconds in real time! Though you may want to send a rescue mission, as your kerbal is now stranded. If you have any questions, feel free to shoot me a message on src, happy flying :)