Here's what I did. Right now the June contract is trading at 10pt. premium to the March contract so I just add 10 pts to it. I look for the high and low for several days and see if it worked at those days too. It is probably not the most scientific way to do it but it has worked for me in the past. I will check the link after I get back from the vacation.
Wouldn't it be simpler to make your decision on SPX, and play whatever contract you want? It's like playing options directionally based on their underlying (obviously keeping an eye on their implied volatility).
I've gone back and forth on how to handle this as well. Until more ES June contract data accumulates over time, I think I'll use S&P Cash for long-term value areas and volume peaks and valleys. It will require some adjustment for the premium, but at least I will be able to tell when the market is approaching a key level.
Range for tomorrow is 1313.25-1314.25. If the market opens higher and my buy-limit order is executed, I'll like to see about 4 pts. profits in an hour after the execution. If the order is executed but the market doesn't move within that time-frame, it is probably a good idea to take the small profit and maybe put a sell-stop at 1213.25. reverse this if the market opens lower.
It was an okay day. Although I made 2.25 pts. it was not good. I had the target at 1321.25 based on my past observations, I do not know why I exited at 1317.5. The high of the day was 1321.5. Instead of making 6 pts. I made 2.25 pts.