After a few days, the yeast will have converted so much sugar to alcohol that it can’t carry on working any more. At this point, the gravity reading will stop falling and the beer is ready to bottle. If working on a small batch, you don’t want to be drawing a fresh sample each day; my set up and choice of yeasts normally takes 4-5 days and I get an indication by monitoring the temperature (lowering yeast activity means the temperature starts falling and the brew belt comes into play more often to keep the level fairly steady). I draw a sample, which is normally near the target final gravity, then leave it next to the fermentor to double check the next day.
You need enough bottles to hold the beer. I normally reckon on getting about 6l of beer to bottle from my 10l of starting water, so I’ll clean and sterilise about 14 500ml bottles to give me a margin of error. Bottle caps sterilised too – and make sure they fit on your bottles (sizes aren’t entirely standardised). Given that volume estimate, you can calculate how much sugar to add for the secondary fermentation inside the bottle. In practise, it works out about 2.5g per bottle for the styles I’m brewing. I dissolve the sugar in my wort sample, put that into my jerry can and siphon the beer out of the fermentor; this time, I do try and minimise the amount of trub that gets in.
The beer can be bottled – a bottling wand is helpful, attached to the siphon – and capped, which can be tricky with only two hands. A dry run with water might not be a bad preparation to work out how to co-ordinate everything without knocking bottles over. Once that’s done, the work is almost over.
Leave the bottles somewhere warm for a week or so; the yeast inside the bottle wants a decent temperature in order to work on that fresh sugar and create some CO2. It is inert, so protects the beer and also gives it a bit of fizz – producing both mouthfeel and the head on top of the glass. Somewhere during that week, you can label the bottles if you want – milk turns out to be perfect for sticking the labels on and you wipe off the excess, so it doesn’t seem to create any sour smells. Put the beer somewhere cool and give it another week or two to condition.