Explanations
I was going to elaborate on it in my first post but I am not 100% sure, so take this with a grain of salt. Also, remember that the volitional form can be used for "let's" but also for "you/I should". Like "doa wo akemashou ka?" does not mean "should we open the door".
1) ~しないでおこう - shinaide okou (okimashou)
Literally: "let's leave that undone" If you know the base form, [shinaide oku] this is a little bit easier to understand. For example "shigoto wo shinaide oku" meaning "to leave one's work unfinished". So this one is something more like "let's move on without doing that"
2) ~ないようにしよう - nai you ni shiyou (shimashou)
literally: "Let's/you should make it so that we/you don't X" This one kind of has a "let's avoid doing x" connotation
3) ~のはやめよう - no wa yameyou (yamemashou)
literally: "Let's/you should stop doing X" This one is often used when changing a plan like "Let's give up on going to the party (cause the traffic is awful, or whatever)" or with suggesting someone should stop doing an action "Why don't you stop smoking."
4) ~のはよそう - no wa yoso (yoshimashou)
litterally: "let's/you should quit/restrain yourself from doing X" This one is used more for resisting or avoiding a certain course of action.
There, clear as mud, right?