A major issue for mine, when trying to build MOCs, is keeping track of parts. If I use parts from a set which is easily distinguishable (for example, among all my sets only one has green parts) it is fine but otherwise I tend to lose track of what part came from where. 

I usually arrange my parts as per official sets because in future I may decide to sell few sets and thus avoid mixing parts into one giant bucket. 

As a consequence, I can't make complex MOCs because that will invariably require mixing up parts among sets. 

I understand some of you buy 2 sets of each, one to display and one for MOC but that option I'd quite expensive. 

Any advise?

PS: I looked at similar threads but they tend to focus on overall organisation of all parts i.e. mixing up parts from different sets. 

you could just find the parts using the parts list in the back of the instruction booklets when you want to sell a set...

Um.... I may not understand it correctly, but you have the instruction books with the parts list for each set.

You also have http://rebrickable.com/ to help you keep track of your whole inventory.

Sorting parts following inventory list is quite painstaking process :(

I already decided that I'd rather sort parts by type than set, even though I don't have much Technic yet. If I need to sell a set, I will find the parts by building it, then check rebrickable to see what extra, unused parts should be in the box. That should work fine.

Sort your parts by type into different storage boxes (i.e. liftarms, axles, plates, pins etc) the use the instruction book or rebrickable to assemble the kits when you want to sell. Shouldn't take more than 20 mins to sort out a set I would have thought.

I usually arrange my parts as per official sets because in future I may decide to sell few sets and thus avoid mixing parts into one giant bucket. 

As a consequence, I can't make complex MOCs

So, what do you find more important in your LEGO hobby? Buliding MOCs, or the idea that you might decide to sell a few sets?

Only you can answer that question. But I can't even imagine this is a tough call for anybody, especially given the fact that all set inventories are simply available.

Only advice I can give is to not mix up old gray and new gray items. Otherwise the best way in my opinion is just to sort the parts according to their type. If you one day decide to sell sets, it's not really a big time sink to sort the parts into sets if you already have them sorted by their type.

Eh? Bricklink.

http://www.bricklink.com

Edited January 26, 201312 yr by andythenorth

Why don't you sort the parts by element or part number? When it comes time to sell the set just build it and compare it to the part list. Sorting by set doesn't make much sense. I used to have somewhat the same issue. I like collecting and displaying the technic sets. One day I said forget it I'm taking it all apart except for a few favorites. I sort everything with akro-mils organizers.

By the way as stated above rebrickable.com is a great site.

I have a few sets built which I keep as they are, everything else is sorted by piece in some divided cases. If I every decide to sell any I build them and sell them like that.

As somebody above said, what is more important to you?

If it were me, I'd just mix up the pieces however you wish to build a moc. When it comes time to sell a set, you could build it, then disassemble it and throw all the parts in a bag. You could throw in a some of the typical extra parts like bushings, lights, etc.

Edited January 26, 201312 yr by dhc6twinotter

Just sort all of your pieces by design, and in some case color. I have all my "rainbow" color pieces in box and my neutral colors in another. If I ever want to build a set back it'll be easy because everything's sorted.

Same here, I have a range of small parts containers and some large parts containers, all sorted by type then colour if there are lots of them. the last time i sold a set was a Model team truck, I have the original instructions so i built the model then took photos and sold it. you will need to build it anyway assuming you are storing broken down, all that remains is a quick check on bricklink to see what extras were included over the main a-model and your done. this way you get to have all your parts when you needed them.