im not interested (need to calm myself lols) but y dont you go by batch. i.e. first batch modular then starwars big set then starwars small set then creator expert etc etc.. not all 400 in one go but start with ones most sought after

Where to sell online: Post in LYN garage sales, Facebook (just search for Lego sales groups), ebay, mudah, bricklink, etc. There are more people looking to buy Lego there than in this thread.

How to sell: You need a list of items you are selling. Price is optional but be prepared to entertain a lot of requests for prices and discounts (this is Malaysia after all ). Also, state your dealing method - COD location, and do you offer postage option for outstation buyers?

Tips:
1) Don't tell people that you are quitting for financial reasons and need to let go by August. You're putting yourself at a disadvantage here, as prospective buyers will take advantage and offer lower prices if they feel you are desperate to sell fast.
2) It's normal for buyers and collectors to shop around for best deals. So expect to entertain a lot of inquiries that do no lead to sales.
3) You say you have 400 sets to let go. That is a big collection. Are you planning to sell everything? Some sets will be easier to sell than others - factors to consider are demand, avaialability (is a set hard to find, retired?), and most importantly, your PRICE.
4) Do your research on market prices for each set. There are many sellers nowadays, so you got to price you items competitively against the market price.
5) Consider how much TIME you want to invest in selling - posting items-for-sale online, communicating with prospective buyers (this takes a lot of time, believe me!), closing the deal (arranging for COD, payments, packing and sending off packages at post office).
6) Consider bulk or bundle offers if you really need to let go your entire collection fast. This will save you lots of time but you must be willing to offer greater discounts to encourage collectors to take up the bulk/bundle offer that may include some undesirable sets like Chima, Ninjago, City, etc.

All the best with your sales. I look forward to seeing your sales list too. (Y)