I think a lot depends on why you are starting the position. If you are creating some balance or a hedge or the second part of a leg, then you may need to chase it a little bit and pay up to prevent the need for chasing it a lot a few minutes later. In these cases, you may have significant exposure and you really need to get filled. In this case, I may enter mid bid/ask and wait a bit for the price to come to me, then chase it and pay up if it starts to move away.
