I don't want to gamble on movements, I want to exploit the difference in prices at different exchanges. Don't think the companies offering leverage give prices for different exchanges.
Can't remember if I mentioned this here or elsewhere and can't be bothered reading through all the pages again to see...
The easiest / most risk free way to do this appears to be taking advantage of the pricing difference between Bitstamp and LocalBitcoins. Its going to require a bit of start up capital to do to any level worth doing though as if you try it for £100 here and there the bank wire fees are going to wipe out any potential profit.
Bitstamp price right now to buy = $484
Locabitcoins price right now to sell = £311
So lets say you start with a float of 10 bit coins. You'd also need to have dollars on Bitstamp ready to immediately place further orders.
List coins for sale on Localbitcoins. If you sell a coin for £311, immediately get on Bitstamp and buy another one for $484. So using xe.com exchange rate, you sold for £311 and immediately replaced it for £290.
The fees are relatively low - 1% and 0.5% or something, so under £5. Lets just assume a fiver... so you made £16 from the transaction.
There are some risks - selling on LBC and then buying on Bitstamp won't be instant. So there might be some fluctuations between your two transactions. These should generally cancel each other out and you can obviously minimise it by placing the trades within seconds of each other.
The other thing is the Bitstamp rate changes 'live', its constantly moving. So you'd need to stay on top of your LBC orders as a price movement could leave you forced to complete an order and then buy it back for the same or less. I'm not a seller on LBC so I don't know if they have any automated tools to match the price up or whatever. If not then you realistically need someone to check in multiple times per hour... it could all be done from an iPad or phone though.
The other risk is either Bistamp or LBC go scam or get hacked - you'd need to leave some coins for trading on LBC and some funds for instant buys on Bitstamp so there is some risk level with that.
Also the other risk is in the pricing of your float - if you buy 10 bit coins to start this off today at $4840, make £1000 trading in a month and the Bitcoin price drops 25%, you've basically lost all of your trading profit. Of course this goes the other way too, you could end up making more money from holding the float than you actually made trading. If you're already holding Bitcoins anyway then you can just ignore this paragraph as you'd have made/lost that amount whether you traded or not...
I've no idea what sort of volume you can do with this though - I really have no idea whether you'd end up struggling to make minimum wage or whether you'd earn a real nice income from it.