If you are trading just one pair, I would place more than one order per direction. Say 4 buy pings and 4 sell pings. Look at the market and try to guess what could be a reasonable price range (max and min) for the next hours-days (good luck with this).
So over the next few days I believe the high for LTC/BTC pair on Poloniex will be .021 and the low to be .0198 what would be a good 4-4 proposal?
Buy: .0198, .01995, .0201, .02025
Sell: .02055, .0207, .02085, .021
As a minimum you should create a stop loss wherever you feel comfortable with, and rise Min % Garanteed Gain a bit. What is a bit? Well, it depends how wide is the range you guessed and how expensive are commissions and fees in your exchange/market. LTC is not one of the currencies with widest daily ranges. I would try with 1% and see how it goes.
So if the current price is .0204, set a stop loss at .0204 - (.0204 * .01) = .020196? This would contradict my prediction above.