I've an idea, shamelessly stolen from many other non bitcoin exchanges.
Start paying liquidity providers - or at least letting them trade for free. You can do this by increasing the trading fee for people demanding liqudity.
This will hugely benefit everyone by massively increasing liquidity and bringing market volatility down. It will also benefit you by increasing trading volumes.
MTGOX is liquidity in the bitcoin world. Sorry, that bitcoin is not big enough for you right now but MTGOX has 10x the liquidity of other exchanges. Paying might bring some more, but it is the other exchanges (that are not now paying) that need to pay just as one of them is.
Free trading is the other way, and crypto did it for a short period and they had much better liquidity during that time. They can not do it forever, but I do not think they did it long enough to have the desired impact.