1. Look at the waveform
When you sample from a song that already got drums on it (maybe an old soul record or so) then it’s pretty easy to see where to make your chops. Just look at the waveform. You can actually see the kicks and snares by looking at the waveform. You see them peak. Kicks got more of a round waveform and snares got more of a steep/sharp waveform if that makes any sense.
2. Use shortcuts
If you’re sampling on software know the shortcuts of your software. It saves a lot of time and you will be able to chop samples a lot faster. I use Pro Tools myself and the cut shortcut on there is CTRL+E
3. Stay close to the samples BPM
No matter how good of a time stretcher you use, you always hear it when stretching too much. So stay close to the samples BPM. And if you want to speed it up or slow it down a lot you should pitch shift the sample till it comes close to the BPM you want to use.
4. Fade in-out
To avoid pops and clicks make small fades at the start and end of your chops.