Quote from jwcapital:
Depending on your broker, you would like to enter both trades simultaneously. My broker ( I trade Future options on the ES (emini S&P 500) does not allow simutaneous entry, for market orders on futures options are not permitted on Globex. So, I ahd to leg in. I shorted the lower premium leg first..once that order was filled, I legged into the higher premium trade. I actually got a better total premium than if I had simultaneous order capability.
You can avoid trading two option legs by trading the synthetic. Sell two calls (puts) and go long (short) one ES spot to effect the synthetic straddle.