Summarize the following:
This trick is great if you need to ash into an empty beer bottle or any glass bottle. It's especially useful because the bottle acts a receptacle for the ash, so you can just throw your ash away with the bottle after you're finished. Make sure you're done with your beverage so you don't end up drinking ash, which could have dangerous health effects. In this grip you're firmly holding it at the filter but not forcefully enough where the filter becomes crushed. Hold the cigarette upright as the ash will easily fall down if it's pointed downwards. Be careful that the tip of the cigarette is hovering over the bottle so the ash falls straight into the bottle. Keep the bottle stationary as well to ensure the ash doesn't fall anywhere else. Flick the bottom of the filter with the fingernail on your middle finger. This will cause the tip of the cigarette to hit the inside of bottle, causing the ash to fall inside the bottle. Flicking the cigarette over for too long while cause it to burn more quickly. It might take a few times to get the ash in the bottle, so make sure to flick the cigarette with enough force to loosen the ash up in a couple tries.
Use this method at bars or at home. Hold the cigarette between thumb and index finger. Turn the cigarette upside down over the bottle's opening. Put the cigarette inside the bottle. Make it quick.