Deranking in CS:GO will happen if you lose too many matches while doing poorly. Deranking depends a whole lot on individual performance and team performance, therefore losing as hard as possible is recommended. We suspect Valve has added some kind "anti-deranking" features to their game, so you must make the losses look like you are legitimately playing bad and deserve to lose your current rank. I recommend taking any map on and running into people, missing almost all of your shots except maybe one or two and hitting them in the feet or something for very low damage.

It is not recommended to queue with less than 5 people to derank with, you might get reported by your teammates and a griefing overwatch ban will result in your account being useless for 29-40 days as it basically acts like a temporary VAC ban (will show as "game ban" on your steam profile).

Try not to get too many headshots in a game and miss as many shots as possible. The worse you do, the better chances of deranking are.

Important:
if you think you're "stuck" and can't derank even after several losses, try playing a real, soloqueue game while still doing badly. That should reset it. I believe this is one of the "anti-deranking" measures Valve has added into their game.

Staying still while not getting kicked for inactivity

+forward; +back

Please use this instead of +forward; +left as it may make your fellow derankers vomit. The above code will make you stay completely still while you still do not get kicked.

Not muting the game if you are tabbed out
snd_mute_losefocus "0"

This part is most simple, you can simply post a comment in the group or create a new discussion in the group and people will add you from there. People do prefer that you mention your rank because a low rank deranking with a higher rank will benefit the higher rank a lot more than the lower one, but do not be discouraged. 0-16 losses are 0-16 losses, and unless the ranks are extremely apart, it will not make an extremely huge difference. You can also use https://derank.me/ for the same.