I have been trading a sim account which always fills orders at the mid price. I am wondering what would be considered a good but reasonably obtainable fill when trading live... mid price? mid price plus a nickle? I am looking at trading calendars, butterflies and verticals on DOW stocks and the spreads can be fairly large.
There's no standard. It depends on the stock, option, market sentiment, order flow, market maker's inventory and etc. Sometimes getting a fill at the mid is "easy", and sometimes it's impossible. Obviously your goal is to get as close to the mid as possible, but sometimes you just have to pay if you want in/out.
look at the volume....high volume stocks normally have high volume options....the higher the volume the more likely you will get a "good" fill, i.e. mid price or better. On options with smaller volume, leave a bid or offer out there for a little while...but you will probably end up just paying the offer price or selling the bid.