Defending against Knights

Hello everyone I just wanted to get some tips from players more experienced than me as far as determining  a quicker way to evaluate knight moves, I notice in a lot of my games my opponent will go out of his way to try and swap his bishops for my knights, i'm guessing he hates playing against them as well Lol,  I have to take my time when there is a crowded board or there are 2 knights attacking in tandem so I don't get forked or hang a piece which makes me time out more than I should, anyone have a rule of thumb to determine all the spaces A knight can go with just a quick look, because I have to run through each spot if especially if my king is near

With a bishop or a rook its pretty easy to see right away