Youtube recommended upload encoding settings

ffmpeg -i <input_file> -codec:v libx264 -crf 18 -bf 2 -flags +cgop -pix_fmt yuv420p -codec:a aac -ar 48000 -b:a 384k -movflags faststart <output_file.mp4>

Streamable recommended Video Settings

ffmpeg -i <input_file> -codec:v libx264 -s hd720 -crf 18 -bf 2 -flags +cgop -pix_fmt yuv420p -codec:a copy -movflags faststart <output_file>.mp4

Note that these settings are the same as in Youtube section, but the keys
-s hd720 was added
-codec:a aac -ar 48000 -b:a 384k was changed to -codec:a copy

ffmpeg -i <input_file> -c copy -ss <time_from> -to <time_to> <output_file>

<time_from> and <time_to> can be in two formats: hh:mm:ss[.xxx] or ss[.xxx]

To concatenate two or more parts, create a file list.txt and add file names like there:

file 'file1.avi'
file 'file2.avi'
file 'file3.avi'

Then execute

ffmpeg -f concat -i .\list.txt -c copy <output_file>