ability to display all of the sRGB gamut and most of the Adobe RGB gamut is important for critical work
detailed high resolution display
if you don't mind giving up battery life, then, consider a 4K display rather than Full HD (1920×1080), especially if you are going for a 13“ or larger screen
touch screen
this could be very useful for:
fine editing with a pen, etc
flicking through your image gallery especially if you can use it as a tablet
good size SSD drive
256Gb should be a bare minimum
512Gb is better
1Gb even better but is very expensive and may be overkill, especially these days when we can use a fast USB 3.0 or 3.1 external drive
fast computer chipset with lots of RAM
aim for a 10th generation quad core Intel i7 or perhaps i5 if you can't afford the i7 (quad core i5 will beat a dual core i7)
the HQ suffix is quad core and although better performance, it runs at 45W not 15W so eats up the battery faster
aim for minimum of 8Gb RAM, preferably 16Gb
fast graphics chipset with lots of RAM
in 2017, an example would be the NVIDIA® GeForce® GTX 1050 with 4GB GDDR5
ports needed for photography
SD card reader preferable (otherwise need a external USB 3 card reader which is a nuisance)
USB 3.1 Thunderbolt port for even faster and more future proof capabilities