- Prepare everything before you get started.
- Make sure your beer is done fermenting before you bottle. If you had a kit and you're bottling after "10 days" per instructions, it might be fine, but it's risky to do it that early unless daily hydrometer readings over 3 days shows 0 change in gravity. Kit instructions are not ideal because they over-simplify/generalize/assume too much.
- Make sure you use the correct amount of carbonation drops for the amount of beer. Over-carbing can cause overly foamy beer or at worst, exploding bottles. If your beer isn't done fermenting, that can also contribute to over-carbing or bottle bombs.
- Don't forget to sanitize everything that is going to touch the beer - hoses, racking cane, bucket, PET bottles/caps, etc.
- Bottle over an open dishwasher or a wide container if you can. Makes cleanup easier, as you'll probably spill some. Have paper towels handy.
- When filling a bottle with the bottle filler, you'll generally fill each bottle to the very top, then pull the filler back out - this will leave exactly the amount of headroom you want per bottle. Also, this is why spilling is all but unavoidable.
- If you're racking to a bottling bucket, keep the cane out of the trub at the bottom. You can't avoid 100% of it, but be dilligent about leaving as much of it in the carboy/fermenter as you can.
- Invest in a Vinator if santizing your bottles is tedious. If you do buy a vinator, take it apart completely for storage or the spring inside will rust up. (I use this one:
http://labelpeelers.com/bottle-rinser-italian-vinator-p-3529.html)
- Leave your caps in a bowl of sanitizer and just pluck them out as you need them. This is based on the assumption that you're using a no-rinse sanitizer (e.g. Star San), though.
- If you are using Star San to sanitize, don't worry about leaving some foam/etc. in your bottles - they say "don't fear the foam" for a reason. Star San is completely ineffective once it dries, and small amounts of Star San (or some foam) in a bottle won't affect your beer flavor. I've had bottles full of Star San foam and just dumped the beer right into it, while others were foam-free. All the beers always taste identical.
- Read Revvy's bottling sticky:
https://www.homebrewtalk.com/f35/bottling-tips-homebrewer-94812/