Normally, I would suggest trading their most active piece during endgames as they won't be able to move that piece a lot, I can't stress how strong knights are in bullet endgames especially when on low time
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Pieces like the bishop take longer time to move, always have show spaces where king can move in the settings selected as it helps you see where to go after an opponent checks you and it takes you a long time to figure out where to go.
There are a few useful bullet tricks that work well when on low time or when your opponent premoves their pieces, the first one is aiming your bishop directly at your opponents queen with the help of a knight. An example would be 1.e4 Nf6 2.g3 d5 (notice that your opponent is premoving so they are likely to make mistakes if they are not good) 3.bf2(this is a mistake since black gains a pawn but it is seen many times in bullet as people like to premove, instead of taking the free pawn on e4) bg4 4. (if they leave their queen hanging, just take it, your opponents will fall into this trap many times.) b3 Bxd1 and their queen is gone. The same tactic can be applied when you fianchetto your bishop(place it on the side of the chess board Bg2 or Bb2 for white and Bg7 and Bb7 for black) where you can just take the rook if your opponent premoves.
Premoves are great but they are the common downfall of many players, always remember to enable premoves and if you premove something and didn't want to premove that, you can simply right click.
Remember to always take freebies and play as fast as possible, do not trade your active pieces and try to play defensively as they would have tricks up their sleeves too. Also, remember to study positions and checkmate puzzles because memorizing a few mates will get you a long way as it guarantees wins in losing positions. Don't think too hard and it's ok if you miss a checkmate, remember that you also have to play against the clock.
30 sec is an easy way to earn rating in bullet, but some people don't have a good mouse or can't play that fast. Don't worry, there are many 2000+ rated players out there who focus on checkmating their opponent in 1 min games, this is easy because people normally make careless mistakes and you can easily win by playing fast during the last 30 seconds or when you have a queen or a rook.