Put everything on his bed, tell him he can't do anything else until his room is clean, it may take all day, but he will clean it eventually.

i would just give him an award say if you clean your room you can go to the party tonight or if you don't clean your room, your party will be cancled

This worked with my kids. I'm a single mom, so one day when I was at my end with the housework, I sat them down and explained that part of the reason I get cranky is that I end up doing so much of the work myself. I instituted the "Magic Three."

When we walk in the door from school, we all pick up and put away three things in three different rooms. Me included. (all the clothes on the floor count as one thing, no matter how many items there are!) In less than 15 minutes, we've picked up and put away a total of 36 things. They get a sense of fairness out of it, there's a designated number of things and a designated time. There are days now when we simply can't find enough things to pick up--which gives them a sense of internal reward, because they begin to realize that "keeping" it clean is much easier than "cleaning."

I think this could work at any age, although if yours is a teen, you might want to skip the cute name!

Have everyone in the house start going into his room and leaving their trash in there and if he comes into their room make sure everyone says keep my room clean...no more toy buying

There are some good articles in regards to that question that can be found here - http://www.thechildtoday.com/Articles/

Teens are held accountable but, if that doesn't work, reverting to methods that work with younger children should be used.

I find that a combination or rewards and also consequences work well in my house. That said, it takes time to set this up and have it working. You may be required to spend the first few months following through on your plan and making sure it is implemented before you can move away from it and let him do it on his own.

Another question might be, what is being modeled? If your partner is not supportive or if you are not following through on things (I don't know what the case is), then the result might be that your son is simply reflecting that back.

rewards are key!

idk how old your son is, but if he is a tween, or above, maybe my suggestion can be modified. rewards charts work very well: say that you make a chart for 7 days that can be hung in his room or the family area. each day that his room is clean (to YOUR standards) he will receive a star or sticker. if he has the entire week full of stickers, he can receive a pre-determined reward at the end off the week. try to make it something you know he would enjoy. even better, have him involved in making his chart and choosing his reward for the week. on a more detailed note, several weeks in a row could earn a trip to a fun/water park--with you, or with you and his friends, depending on your level of enthusiasm!! good luck!

How about if you were to tell him that he doesn't need to clean his room anymore if he doesn't want to and you are not going to tell him to either. But, under two conditions, he must have his room cleaned when family or visitors are coming over and he must clean up after himself in the rest of the house and do his chores.

bribe him...
positive reinforcement of negative reinforcement usually works pretty well... Behvavior modification 101

My first question is, what's in it for him? If you make it reward based he'll do it. Maybe say, if you clean you can watch tv or if you clean you get a dollar (depending on age).